WO2018052038A1 - Positive electrode active material for nonaqueous electrolyte secondary batteries, method for producing same and nonaqueous electrolyte secondary battery using said positive electrode active material - Google Patents

Positive electrode active material for nonaqueous electrolyte secondary batteries, method for producing same and nonaqueous electrolyte secondary battery using said positive electrode active material Download PDF

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WO2018052038A1
WO2018052038A1 PCT/JP2017/033117 JP2017033117W WO2018052038A1 WO 2018052038 A1 WO2018052038 A1 WO 2018052038A1 JP 2017033117 W JP2017033117 W JP 2017033117W WO 2018052038 A1 WO2018052038 A1 WO 2018052038A1
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positive electrode
lithium
active material
electrode active
particles
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PCT/JP2017/033117
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French (fr)
Japanese (ja)
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充 山内
小向　哲史
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住友金属鉱山株式会社
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Priority to CN201780068809.XA priority Critical patent/CN109997260B/en
Priority to EP17850939.4A priority patent/EP3514867B1/en
Priority to US16/332,087 priority patent/US11196048B2/en
Publication of WO2018052038A1 publication Critical patent/WO2018052038A1/en

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    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • H—ELECTRICITY
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    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • C01G53/00—Compounds of nickel
    • C01G53/006—Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen
    • H—ELECTRICITY
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    • H01M4/362—Composites
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    • H—ELECTRICITY
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the positive electrode active material.
  • a high output secondary battery is strongly desired as a battery for electric vehicles including hybrid vehicles.
  • a battery for an electric vehicle is used in a wide temperature range from a high temperature to a very low temperature, and thus requires a high output in such a wide temperature range.
  • non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries as secondary batteries that satisfy such requirements.
  • a non-aqueous electrolyte secondary battery includes a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material of the negative electrode and the positive electrode.
  • non-aqueous electrolyte secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are 4V. Since a high voltage can be obtained, it has been put to practical use as a battery having a high energy density.
  • lithium cobalt composite oxide LiCoO 2
  • lithium nickel composite oxide LiNiO 2
  • nickel composite oxide LiNiO 2
  • Lithium nickel cobalt manganese composite oxide LiNi 1/3 Co 1/3 Mn 1/3 O 2
  • lithium manganese composite oxide LiMn 2 O 4
  • lithium nickel manganese composite oxide LiNi 0. 5 Mn 0.5 O 2
  • lithium composite oxide such as have been proposed.
  • Lithium nickel cobalt manganese composite oxide is a layered compound similar to lithium cobalt composite oxide and lithium nickel composite oxide, and basically has a composition ratio of 1: 1: 1 at the transition metal site between nickel, cobalt and manganese. Including.
  • Lithium nickel cobalt manganese composite oxide (LiNi 0.33 Co 0.33 Mn 0.33 O 2 ) is a lithium cobalt composite oxide (LiCoO). As compared with 2 ), there is a problem that resistance is high and high output is difficult to obtain.
  • LiCoO lithium cobalt composite oxide
  • Patent Document 1 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide, wherein the lithium transition metal composite oxide includes primary particles and aggregates thereof. It exists in the form of particles comprising one or both of secondary particles, the primary particles have an aspect ratio of 1 to 1.8, and at least the surface of the particles is composed of molybdenum, vanadium, tungsten, boron, and fluorine.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery having a compound having at least one selected from the group has been proposed. By having a compound having at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on the surface of the particles, the conductivity is improved.
  • Patent Document 2 discloses a compound containing, as a main component, a lithium transition metal compound having a function capable of inserting and removing lithium ions, and containing at least one element selected from B and Bi as the main component material And a lithium transition metal-based compound powder for a lithium secondary battery positive electrode material, which is fired after adding a compound containing at least one element selected from Mo, W, Nb, Ta and Re Has been proposed. After adding the additive element in combination, firing is performed to obtain a lithium transition metal-based compound powder composed of fine particles with suppressed grain growth and sintering, and the rate and output characteristics are improved. It is said that a lithium-containing transition metal compound powder that is easy to prepare an electrode can be obtained.
  • Patent Document 3 discloses a general formula Li a Ni 1-xy Co x M 1 y W z M 2 w O 2 (1.0 ⁇ a ⁇ 1.5, 0 ⁇ x ⁇ 0.5, 0 ⁇ y ⁇ 0.5, 0.002 ⁇ z ⁇ 0.03, 0 ⁇ w ⁇ 0.02, 0 ⁇ x + y ⁇ 0.7, M 1 is at least one selected from the group consisting of Mn and Al, M 2 is A non-aqueous electrolyte comprising a lithium transition metal composite oxide represented by at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, and Mo) and a boron compound containing at least a boron element and an oxygen element
  • a positive electrode composition for a secondary battery has been proposed. By using a positive electrode composition containing a lithium transition metal composite oxide containing nickel and tungsten and a specific boron compound, the output characteristics and cycle characteristics of the positive electrode composition using the lithium transition metal composite
  • Patent Document 4 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered crystal structure lithium transition metal composite oxide, wherein the lithium transition metal composite oxide is a particle, and at least A positive electrode active material for a non-aqueous electrolyte secondary battery having lithium borate on the surface of the particles has been proposed. By having lithium borate on the surface of the particles, it is possible to improve the thermal stability while maintaining the same initial discharge capacity and initial efficiency.
  • Patent Document 5 at least one of a sulfate and a boric acid compound is deposited on a composite oxide particle containing lithium (Li) and at least one of nickel (Ni) and cobalt (Co). And a step of heat-treating the composite oxide particles deposited on at least one of the sulfate and boric acid compounds in an oxidizing atmosphere.
  • a positive electrode active material capable of realizing an increase in capacity of a secondary battery and an improvement in charge / discharge efficiency can be manufactured.
  • Patent Document 6 discloses Li a Ni x Co y Al z O 2 (where Ni is Mn, Cr, Fe, It can be substituted with one or more metal elements selected from the group consisting of V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce.
  • a, x, y, and z are 0.3 ⁇ a ⁇ 1.05, 0.60 ⁇ x ⁇ 0.90, 0.10 ⁇ y ⁇ 0.40, 0.01 ⁇ z ⁇ 0.
  • the boric acid compound is deposited on the composite oxide particles whose average composition is expressed by the following formula:
  • the carbonate ion content is 0.15 wt% or less, and the borate ion content is 0.01 wt% or more and 5.0 wt%.
  • % Positive electrode active material is proposed.
  • the present invention has been made in view of these circumstances, and improves the output characteristics and battery capacity when used in a non-aqueous electrolyte secondary battery, and the gelation of the positive electrode mixture paste during electrode production. It aims at providing the positive electrode active material which suppressed. Moreover, an object of this invention is to provide the method which can manufacture such a positive electrode active material easily in industrial scale production.
  • the present inventor causes a specific amount of a boron compound to be present on the primary particle surface of the lithium nickel cobalt manganese composite oxide constituting the positive electrode active material, and the primary particles.
  • the amount of water-soluble Li present on the surface into a specific range, the output characteristics and battery capacity of a secondary battery using this positive electrode active material for the positive electrode are improved, and the gelation of the positive electrode mixture paste is suppressed.
  • the knowledge that it is possible to achieve both has been obtained, and the present invention has been completed.
  • the average particle diameter of the secondary particles is 3 ⁇ m or more and 20 ⁇ m or less. Moreover, it is preferable that the average particle diameter of a primary particle is 0.2 micrometer or more and 0.5 micrometer or less. Further, it is preferable that [(d90 ⁇ d10) / average particle diameter], which is an index indicating the spread of the particle size distribution of the secondary particles, is 0.60 or less.
  • the secondary particles preferably have a hollow structure in which a hollow portion is formed.
  • the boron raw material is at least one of boron oxide and boron oxo acid. Moreover, it is preferable that a boron raw material is orthoboric acid. Moreover, you may further provide the crushing process which crushes the lithium nickel cobalt manganese complex oxide particle obtained at the baking process.
  • a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein the positive electrode includes the positive electrode active material for the nonaqueous electrolyte secondary battery.
  • the positive electrode active material of the present invention When used for the positive electrode of a non-aqueous electrolyte secondary battery, excellent output characteristics and high battery capacity can be obtained. Moreover, the positive electrode active material of the present invention can suppress gelation of the positive electrode mixture paste during electrode production, and can facilitate the production of a non-aqueous electrolyte secondary battery.
  • the method for producing a positive electrode active material of the present invention can be easily implemented even in industrial scale production and is extremely useful industrially.
  • FIG. 1A and 1B are diagrams showing an example of the positive electrode active material of the present embodiment.
  • FIG. 2 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment.
  • FIG. 3 is a photograph (observation magnification 1000 times) showing an example of the observation result of the positive electrode active material of the present embodiment by a scanning electron microscope.
  • 4 (A) and 4 (B) are photographs showing examples of the results of analysis by soft X-ray emission spectroscopy of the cross section of the positive electrode active material of the present embodiment.
  • 5A to 5C are graphs showing the evaluation results of the positive electrode active materials obtained in Examples and Comparative Examples.
  • FIG. 6 is a schematic diagram showing the structure of the coin battery used for the evaluation.
  • FIG. 7 is a diagram illustrating an example of a Nyquist plot.
  • FIG. 8 is a diagram showing an equivalent circuit used for impedance evaluation.
  • the positive electrode active material for a non-aqueous electrolyte secondary battery, the manufacturing method thereof, and the positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment will be described.
  • some parts are emphasized or some parts are simplified, and actual structures, shapes, scales, and the like may be different.
  • FIG. 1 is a schematic diagram showing an example of a positive electrode active material 10 for a non-aqueous electrolyte secondary battery (hereinafter also referred to as “positive electrode active material 10”) according to the present embodiment. is there.
  • the positive electrode active material 10 includes lithium nickel cobalt manganese composite oxide 1 (hereinafter also referred to as “lithium metal composite oxide 1”).
  • the lithium composite metal oxide 1 includes a secondary particle 3 in which a plurality of primary particles 2 are aggregated, and a boron compound 4 containing lithium present on at least a part of the surface of the primary particle 2 (hereinafter referred to as “lithium boron compound 4”).
  • the amount of water-soluble Li present on the surface of the primary particles 2 is 0.1% by mass or less based on the total amount of the positive electrode active material.
  • the positive electrode active material 10 is a positive electrode in a non-aqueous electrolyte secondary battery (hereinafter also referred to as “secondary battery”) using the positive electrode active material 10 by allowing the lithium boron compound 4 to be present on the surfaces of the primary particles 2.
  • the reaction resistance hereinafter also referred to as “positive electrode resistance”
  • the initial charge capacity hereinafter also referred to as “battery capacity”
  • the positive electrode resistance of the secondary battery the voltage lost in the secondary battery is reduced, and the voltage actually applied to the load side becomes relatively high, so a high output is obtained. .
  • the voltage applied to the load side is increased, lithium is sufficiently inserted and extracted from the positive electrode, and thus the battery capacity is considered to be improved.
  • the lithium boron compound 4 formed on the surface of the primary particles 2 has high lithium ion conductivity and the movement of lithium ions. Therefore, in the positive electrode of the secondary battery, a Li conduction path is formed at the interface between the electrolytic solution and the positive electrode active material 10 to reduce the positive electrode resistance, thereby improving the battery output characteristics and the battery capacity. it is conceivable that.
  • the lithium boron compound 4 has a form of, for example, a lithium boron composite oxide.
  • the positive electrode active material 10 has the lithium boron compound 4 on the surface of the primary particle 2 and the amount of water-soluble Li existing on the surface of the primary particle 2 is 0.1% by mass or less. Gelation of the positive electrode mixture paste (hereinafter also referred to as “paste”) using the active material 10 can be suppressed.
  • the amount of water-soluble Li existing on the surface of the primary particles 2 refers to the amount of Li eluted in water when the positive electrode active material 10 is dispersed in water.
  • the amount of water-soluble Li includes the excess lithium compound present on the surface of the primary particles 2 described above, Li derived from the lithium boron compound 4 is included. And the present inventors discovered that gelation of a paste was suppressed by forming the lithium boron compound 4 in the surface of the primary particle 2 so that water-soluble Li amount may become the said range.
  • the gelation of the positive electrode mixture paste is caused by excess lithium compounds such as lithium hydroxide and lithium carbonate that are present on the surface of the primary particles of the lithium composite metal oxide being eluted in the water contained in the positive electrode mixture paste. It is believed to be caused by raising the pH value of the paste.
  • a boron raw material that is one of the raw materials of the lithium boron compound 4 is a lithium metal composite in the manufacturing process of the positive electrode active material 10. It is considered that the gel of the paste is suppressed by reacting with an excess lithium compound present on the surface of the primary particles in the oxide particles (raw material) to form the lithium boron compound 4.
  • the amount of water-soluble Li on the surface of the primary particle 2 exceeds 0.1% by mass with respect to the total amount of the positive electrode active material 10, an effect of suppressing gelation of the paste cannot be obtained.
  • the details of the cause are unknown, it is considered that the lithium boron compound 4 is excessively formed on the surface of the primary particle 2 and the water-soluble lithium compound contributing to gelation increases.
  • the boron raw material reacts with the surplus lithium compound on the surface of the primary particles of the lithium metal composite oxide particles (raw material), and the crystal of the lithium metal composite oxide particles (raw material). It is thought to react with lithium extracted from the inside. Therefore, when the lithium boron compound 4 is excessively formed, lithium ions contributing to charge / discharge are reduced, and the battery capacity of the secondary battery is also reduced.
  • the surface of the primary particle 2 refers to the surface of the primary particle 2 that can be in contact with the electrolytic solution in the positive electrode of the secondary battery.
  • the lithium boron compound 4 is formed on the surface of the primary particle 2 that can be in contact with the electrolytic solution, thereby reducing the positive electrode resistance and improving the output characteristics and the battery capacity.
  • the surface of the primary particle 2 has an electrolyte solution that communicates with the surface of the primary particle 2 a exposed on the outer surface (surface) of the secondary particle 3 or the surface of the secondary particle 3.
  • the surface of the primary particle 2b inside the permeable secondary particle 3 is included.
  • the surface of the primary particle 2 includes the boundary between the primary particles 2 as long as the primary particles 2 are incompletely bonded and the electrolyte solution can permeate. Moreover, the surface of the primary particle 2 contains the surface of the primary particle 2c exposed to the hollow part 5 (space
  • the presence of the lithium boron compound 4 on the surface of the primary particle 2a exposed on the surface of the secondary particle 3 can be confirmed by, for example, X-ray photoelectron spectroscopy (XPS). Further, the presence of boron on the surface of the primary particles 2b and 2c inside the secondary particle 3 is determined by, for example, a soft X-ray emission spectroscopy apparatus (Soft X-ray emission spectroscopy) attached to a field emission scanning electron microscope (FE-SEM). SXES).
  • Soft X-ray emission spectroscopy Soft X-ray emission spectroscopy apparatus attached to a field emission scanning electron microscope (FE-SEM). SXES).
  • lithium is considered as an element that forms a compound with boron, and the secondary particles 3 Considering that at least part of boron is present in the form of lithium boron compound 4 on the surface of primary particles 2a exposed on the surface, even on the surfaces of primary particles 2b and 2c inside secondary particles 3, It is estimated that the lithium boron compound 4 (for example, lithium boron complex oxide) is formed.
  • the lithium boron compound 4 may be present on a part of the surface of the primary particle 2 or may cover the entire surface of the primary particle 2. If the lithium boron compound 4 is present on at least a part of the surface of the primary particle 2, the effect of reducing the positive electrode resistance can be obtained.
  • the lithium boron compound 4 is preferably fixed to the surface of the primary particle 2. Thereby, the electroconductivity with the lithium boron compound 4 and the primary particle 2 of lithium composite oxide can be improved more, and the reduction effect of positive electrode resistance is acquired more. In addition, as shown in FIGS.
  • the lithium boron compound 4 includes not only the surface of the primary particles 2 a existing on the surface of the secondary particles 3 but also the primary particles 2 b inside the secondary particles 3, It is preferable that it is formed also on the surface of 2c.
  • the lithium boron compound 4 is formed on the surfaces of the primary particles 2b and 2c in the secondary particle 3, the movement of lithium ions can be further promoted.
  • a part of boron (B) in the lithium metal composite oxide 1 may be dissolved in the crystal of the lithium metal composite oxide 1. However, if all the boron is dissolved in the crystal of the lithium metal composite oxide 1, the effect of reducing the positive electrode resistance cannot be obtained. Further, when boron is dissolved in the lithium metal composite oxide 1, the battery capacity may be greatly reduced.
  • the amount of water-soluble Li on the surface of the primary particles 2 is 0.1% by mass or less with respect to the total amount of the positive electrode active material 10.
  • the positive electrode active material 10 of the present embodiment suppresses gelation of the positive electrode mixture paste by forming the lithium boron compound 4 on the surfaces of the primary particles 2 and the amount of water-soluble Li being in the above range. it can.
  • the total amount of the positive electrode active material means the total amount of the primary particles 2, the secondary particles 3, the lithium boron compound 4, and a compound containing lithium other than the lithium boron compound present on the surface of the primary particles 2.
  • the minimum of the amount of water-soluble Li is 0.01 mass% or more with respect to the positive electrode active material whole quantity, for example.
  • the amount of water-soluble Li in the positive electrode active material 10 is, for example, the amount of boron raw material added in the boron mixing step (step S40) or the heat treatment temperature in the heat treatment step (step S50) in the manufacturing process of the positive electrode active material 10 described later. By appropriately adjusting the value, it is possible to control within the above range.
  • the amount of water-soluble Li present on the surfaces of the primary particles 2 is determined by neutralizing titration of the water-soluble Li eluted in pure water after adding pure water to the positive electrode active material 10 and stirring for a certain time with hydrochloric acid or the like. This is a value that can be calculated.
  • the positive electrode active material 10 may have an increased amount of water-soluble Li as compared with a lithium metal composite oxide not containing the lithium boron compound 4.
  • 5A to 5C show the initial discharge capacity (FIG. 5A) and the positive electrode resistance (FIG. 5B) of secondary batteries using the positive electrode active materials obtained in Examples and Comparative Examples described later. )) And the amount of water-soluble Li (FIG. 5C).
  • the positive electrode active material obtained in the example has an increased amount of water-soluble Li compared to the positive electrode active material of Comparative Example 1 that does not contain boron (B). Yes.
  • lithium boron compound 4 This is considered to reflect an increase in the amount of the lithium boron compound 4 present on the surface of the primary particles 2, and the boron raw material not only reacts with excess lithium, but also lithium metal composite oxide particles (raw material). It can be considered that this is because lithium boron compound 4 is formed by reacting with lithium extracted from the inside crystal.
  • the lithium metal composite oxide 1 has a hexagonal layered crystal structure, and the crystallinity thereof is determined by, for example, the length of the c-axis (hereinafter referred to as “c” obtained by performing a Rietveld analysis of the X-ray diffraction result. It can also be evaluated based on the lithium site occupancy at the lithium site in the crystal (hereinafter sometimes referred to as “Li site occupancy”).
  • the Li seat occupancy of the lithium metal composite oxide 1 is preferably 96% or more, and more preferably 96.5% or more.
  • the Li seat occupancy is controlled within the above range, lithium deficiency at the lithium site can be suppressed and the crystallinity of the lithium composite oxide particles can be maintained high. Thereby, while improving the output characteristic of the obtained secondary battery, high battery capacity can be maintained.
  • the said General formula (1) shows the composition of the positive electrode active material 10 whole containing the secondary particle 3 and the lithium boron compound 4 which exists in the surface of the primary particle 2.
  • FIG. The content of each element can be measured by ICP emission spectroscopy.
  • the range of t indicating the boron content is 0.02 ⁇ t ⁇ 0.04. Further, as described above, at least a part of boron is present as a lithium boron compound on the surface of the primary particle 2.
  • t is in the above range, when the positive electrode active material 10 is used for the positive electrode of the secondary battery, the effect of sufficiently reducing the positive electrode resistance can be obtained and a high battery capacity can be obtained, and the paste can be gelled. Can be suppressed.
  • t is less than 0.02, the effect of sufficiently reducing the positive electrode resistance cannot be obtained, and gelation of the paste cannot be suppressed.
  • the range of t is preferably 0.025 ⁇ t ⁇ 0.04.
  • x indicating the content of nickel is 0.1 ⁇ x ⁇ 0.5, preferably 0.20 ⁇ x ⁇ 0.50. That is, the lithium metal composite oxide 1 contains nickel as a metal element, and the nickel content is 10 to 50 atom%, preferably 20 atoms, with respect to the total of metal elements other than lithium (excluding B). % Or more and 50 atom% or less.
  • the primary particles 2 constituting the lithium metal composite oxide 1 have a layered rock salt type crystal structure.
  • y indicating the cobalt content is 0.1 ⁇ y ⁇ 0.5, and preferably 0.15 ⁇ y ⁇ 0.45. That is, the lithium metal composite oxide 1 has a cobalt content of 10 atomic% to 50 atomic%, preferably 15 atomic% to 45 atomic%, based on the total of metal elements other than lithium (excluding B). It is. When the cobalt content is in the above range, it has high crystal structure stability and is more excellent in cycle characteristics.
  • z indicating the manganese content is 0.1 ⁇ z ⁇ 0.5, and preferably 0.15 ⁇ y ⁇ 0.45. That is, the manganese content is 10 atom% or more and 50 atom% or less, preferably 15 atom% or more and 45 atom% or less with respect to the total of metal elements other than lithium (excluding B). When the manganese content is in the above range, high thermal stability can be obtained.
  • an element M1 other than Li, Ni, Co, Mn, and B may be added.
  • the element M1 may be a metal element, and the element M1 contains one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Fe, and W. May be.
  • the general formula (1) is expressed by the general formula (1) ′: Li 1 + s Ni x Co y Mn z B t O 2 + ⁇ (in the formula (1) ′, ⁇ 0.
  • ⁇ may be 0.
  • the average particle diameter of the positive electrode active material 10 is preferably 3 ⁇ m or more and 20 ⁇ m or less, and more preferably 4 ⁇ m or more and 15 ⁇ m or less.
  • the obtained secondary battery can further achieve both high output characteristics and high battery capacity, and high filling ability to the positive electrode.
  • the average particle size is less than 3 ⁇ m, high filling property to the positive electrode may not be obtained, and when the average particle size exceeds 20 ⁇ m, high output characteristics and battery capacity may not be obtained.
  • the average particle size of the primary particles 2 is preferably 0.2 ⁇ m or more and 1.0 ⁇ m or less, and more preferably 0.3 ⁇ m or more and 0.7 ⁇ m or less. Thereby, higher output characteristics and battery capacity when used for the positive electrode of the battery, and higher cycle characteristics can be obtained.
  • the average particle size of the primary particles is less than 0.2 ⁇ m, high cycle characteristics may not be obtained, and when the average particle size exceeds 0.7 ⁇ m, high output characteristics and battery capacity may not be obtained.
  • the average particle diameter of the primary particles 2 can be measured by observing the cross section of the secondary particles 3 with a scanning electron microscope (hereinafter also referred to as “SEM”).
  • SEM scanning electron microscope
  • a sample in which the composite hydroxide 1 is embedded in a resin or the like is cut to prepare a sample of the cross-section of the secondary particles 3. This is done by observing.
  • the secondary particle 3 to be observed has a laser beam that has a distance d (see FIG. 1) between two points that has the maximum distance on the outer periphery of the cross section of one secondary particle 3 in the cross section of the plurality of secondary particles 3.
  • 20 or more secondary particles 3 which are 80% or more of the volume average particle diameter (MV) measured using a diffraction scattering particle size analyzer are arbitrarily (randomly) selected. Then, 50 or more primary particles 2 are selected arbitrarily (randomly) from each selected secondary particle 3. The longest diameter of the selected primary particle 2 is measured to determine the particle size. For 50 primary particles 2, the obtained particle diameters (longest diameter) are averaged to calculate the particle diameter (average) of primary particles 2 per secondary particle 3. Furthermore, the average particle diameter of the primary particles 2 of the whole positive electrode active material is calculated by averaging the calculated particle diameters (average) of the respective primary particles 2 for the selected 20 secondary particles 3.
  • [(d90 ⁇ d10) / average particle diameter] which is an index indicating the spread of the particle size distribution of the positive electrode active material 10.
  • [(d90 ⁇ d10) / average particle diameter] is 0.55 or less.
  • the minimum value of (d90-d10) / average particle size] is 0. About 25.
  • the spread of the particle size distribution should be within the above range by, for example, performing crystallization by a two-stage crystallization process in the manufacturing process of the positive electrode active material described later to obtain a nickel composite hydroxide as a precursor. Can do.
  • D10 is the number of particles in each particle diameter accumulated from the smaller particle diameter side, and the accumulated volume is Similarly, D90 means the particle size that accumulates the number of particles and the accumulated volume becomes 90% of the total volume of all particles.
  • the average particle diameter of a positive electrode active material means a volume average particle diameter (Mv). The average particle diameters D90 and D10 can be measured using a laser light diffraction / scattering particle size analyzer.
  • the positive electrode active material 10 may have a hollow structure in which the secondary particles 3 form hollow portions 5 in the grains, as shown in FIG. 1B, for example.
  • the secondary particles 3 having a hollow structure can be obtained by using, for example, lithium metal composite oxide particles produced by a method disclosed in Patent Document 6 as a raw material.
  • the electrolyte can be more easily penetrated into the particles of the secondary particles 3, and high output characteristics can be obtained more easily.
  • the hollow portion 5 may be one or plural.
  • the hollow structure also includes a porous structure having a large number of voids in the secondary particles 3.
  • the positive electrode active material 10 includes the lithium metal composite oxide 1 composed of the secondary particles 2 formed by aggregating a plurality of primary particles 1.
  • the positive electrode active material 10 did not aggregate as the secondary particles 2.
  • a small amount of primary particles 1 such as primary particles 1 or primary particles 1 dropped from secondary particles 2 after aggregation may be included.
  • the positive electrode active material 10 may contain lithium metal composite oxide other than the lithium metal composite oxide 1 mentioned above in the range which does not inhibit the effect of this invention.
  • lithium nickel cobalt manganese composite oxide hereinafter also referred to as “lithium metal composite oxide” having a hexagonal layered crystal structure.
  • a positive electrode active material for a secondary battery (hereinafter also referred to as “positive electrode active material”) can be produced.
  • the positive electrode active material 10 can be easily manufactured with high productivity on an industrial scale.
  • the manufacturing method of this embodiment is demonstrated with reference to FIG.1 and FIG.2.
  • the production method of the present embodiment is a crystallization step of obtaining nickel cobalt manganese composite hydroxide particles (hereinafter also referred to as “composite hydroxide particles”) having a specific composition by crystallization.
  • Step S10 a lithium mixing step in which a lithium compound is mixed with the composite hydroxide particles to obtain a lithium mixture (Step S20), and the lithium mixture is fired to obtain lithium nickel cobalt manganese composite oxide particles
  • Step S40 and a heat treatment step (Step S50) for heat-treating the boron mixture.
  • the production method of the present invention will be described in detail.
  • the crystallization process (step S10) is performed by using the general formula (2): Ni x Co y Mn z M2 u (OH) 2 + ⁇ (wherein M2 is an element other than Li, Ni, Co, and Mn.
  • M2 is an element other than Li, Ni, Co, and Mn.
  • the crystallization method is not particularly limited, and a known crystallization method can be used.
  • the composite hydroxide particles obtained by a normal crystallization method are composed of secondary particles in which a plurality of primary particles are aggregated, and the positive active material obtained using the composite hydroxide particles is also aggregated in a plurality of primary particles.
  • the secondary particles are made up of.
  • the crystallization method for example, when composite hydroxide particles are produced industrially by a crystallization method, a continuous crystallization method can be used.
  • the continuous crystallization method can easily produce a large amount of composite hydroxide particles having the same composition.
  • the continuous crystallization method has a problem that the particle size distribution of the obtained product tends to be a relatively wide normal distribution, and particles having a uniform particle size cannot always be obtained.
  • fine powder of less than 3 ⁇ m is mixed. , Easy to cause deterioration of cycle characteristics.
  • the particle size is not uniform, the positive electrode resistance increases, which may adversely affect the battery output.
  • the crystallization process (step S10) as disclosed in Patent Document 5 is clearly defined as a nucleation process and a particle growth process. It is preferable to obtain a composite hydroxide particle having a narrow particle size distribution by separating the particles into a uniform particle size.
  • a crystallization method separated into a nucleation step and a particle growth step will be described.
  • a mixed aqueous solution (hereinafter, also referred to as “mixed aqueous solution”) containing nickel, cobalt, manganese, and optionally an additional element M is prepared.
  • the mixed aqueous solution is prepared, for example, by dissolving a readily water-soluble nickel salt, cobalt salt, manganese salt, and optionally a salt of the additive element M in water at a predetermined ratio.
  • nickel salt, cobalt salt, and manganese salt sulfate is preferably used.
  • an aqueous solution containing the salt of the additive element M is prepared and supplied to the reaction solution described later separately from the mixed aqueous solution. May be.
  • the mixed aqueous solution and the aqueous solution containing an ammonium ion supplier are supplied to the reaction tank while stirring to form a reaction liquid in the reaction tank, and at the same time, an alkaline aqueous solution is supplied to adjust the pH value of the reaction liquid Is controlled to be constant.
  • an alkaline aqueous solution is supplied to adjust the pH value of the reaction liquid Is controlled to be constant.
  • the pH value of the reaction solution is adjusted so as to be 12.0 or more, preferably 12.0 or more and 14.0 or less as a pH value based on a liquid temperature of 25 ° C.
  • the pH value is in the above range, fine nuclei of composite hydroxide particles can be selectively generated in the reaction solution.
  • the pH value is less than 12.0, nucleus growth also occurs at the same time, so that the particle size distribution is likely to be widened, and the total number of nuclei is insufficient and the particle diameter is likely to become coarse.
  • the total number of nuclei can be controlled by the pH and ammonia concentration in the nucleation step and the amount of the mixed aqueous solution supplied.
  • the ammonia concentration in the reaction solution is preferably maintained at a constant value within a range of 3 g / L to 15 g / L.
  • the solubility of metal ions can be kept constant, so that ordered hydroxide particles can be formed and the formation of gel-like nuclei is also suppressed.
  • the particle size distribution can be controlled within a predetermined range.
  • the ammonia concentration exceeds 15 g / L, the composite hydroxide particles are densely formed, so that the positive electrode active material finally obtained also has a dense structure and the specific surface area may be low.
  • the temperature of the reaction solution is preferably set to 35 ° C. or more and 60 ° C. or less.
  • the solubility of the metal ions supplied at a low temperature cannot be sufficiently obtained, and nucleation is likely to occur, and it becomes difficult to control the nucleation.
  • the temperature of the reaction liquid exceeds 60 ° C., the volatilization of ammonia is promoted, so that ammonia for complex formation becomes insufficient, and the solubility of metal ions tends to decrease in the same manner.
  • about pH value and crystallization time in a nucleation process it can set arbitrarily by the average particle diameter of the target composite hydroxide particle.
  • the reaction solution is controlled to have a pH value of 10.5 or more and 12.0 or less as a pH value based on a liquid temperature of 25 ° C. and lower than that in the nucleation step.
  • a pH value 10.5 or more and 12.0 or less as a pH value based on a liquid temperature of 25 ° C. and lower than that in the nucleation step.
  • part of the liquid components in the reaction solution is discharged out of the reaction tank to increase the composite hydroxide particle concentration in the reaction solution, and then continue particle growth. It is also possible. By carrying out like this, the particle size distribution of particle
  • the particle structure of the positive electrode active material obtained using the composite hydroxide particles can be controlled. That is, by controlling the oxygen concentration of the atmosphere, it is possible to control the size of the primary particles constituting the composite hydroxide particles, and it is possible to control the compactness of the composite hydroxide particles. . Therefore, by reducing the oxygen concentration in the reaction vessel to make a non-oxidizing atmosphere, the denseness of the composite hydroxide particles becomes higher, and the resulting positive electrode active material also becomes denser and has a solid structure. become.
  • the denseness of the composite hydroxide particles decreases, and the resulting positive electrode active material has a hollow structure or a porous structure.
  • the inside of the reaction vessel an oxidizing atmosphere at the initial stage of the nucleation step and the particle growth step, and then controlling to a non-oxidizing atmosphere, the denseness of the center portion of the composite hydroxide particles is lowered, and the outer peripheral portion The denseness can be increased.
  • the positive electrode active material obtained from such composite hydroxide particles has a hollow structure having a sufficiently large hollow portion. The size of the hollow portion can be controlled by adjusting the time for the oxidizing atmosphere and the time for the non-oxidizing atmosphere.
  • M2 may or may not contain B.
  • M2 may be a metal element, or may be one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Fe, and W.
  • ⁇ is a coefficient that changes according to the valence of the metal element contained in the composite hydroxide.
  • the composition ratio of the metal element in the composite hydroxide particle is the lithium composite oxide particle constituting the positive electrode active material, that is, the metal element of the lithium metal composite oxide particle (raw material) in which the lithium boron compound is present on the primary particle surface. The composition ratio is maintained. Therefore, the composition ratio of the composite hydroxide particles is adjusted to be the composition ratio of the lithium composite oxide particles.
  • the lithium mixing step (step S20) is a step of obtaining a lithium mixture by mixing the composite hydroxide particles and the lithium compound.
  • the lithium compound content in the lithium mixture is such that the ratio of the number of atoms of Li (Li) to the total number of atoms (Me) of the metal elements other than lithium in the above general formula (2) (Li / Me) is 0.95. Mix so that it is 1.20 or less.
  • Li / Me is less than 0.95, the positive electrode resistance in the secondary battery increases and the output characteristics deteriorate.
  • Li / Me exceeds 1.20, the initial discharge capacity of the secondary battery is reduced and the positive electrode resistance is also increased. From the viewpoint of obtaining a high discharge capacity and excellent output characteristics, it is preferable to mix Li / Me so as to be 1.00 or more and 1.15 or less.
  • the lithium compound is not particularly limited, and a known one can be used.
  • lithium hydroxide, lithium carbonate, or a mixture thereof can be suitably used. From the viewpoint of ease of handling and quality stability, it is more preferable to use lithium carbonate as the lithium compound.
  • the composite hydroxide particles and the lithium compound are sufficiently mixed.
  • a general mixer can be used.
  • a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used, and the complex acid hydrate particles are not destroyed. What is necessary is just to fully mix with a lithium compound.
  • the composite hydroxide particles are heat-treated before mixing with the lithium compound to convert at least a part of the composite hydroxide particles into composite oxide particles. Also good. By converting to composite oxide particles, the amount of water contained when mixing with the lithium compound becomes constant, and Li / Me is stabilized.
  • the manufacturing method of this embodiment includes the process of heating a composite hydroxide particle and removing a part of water
  • the heating temperature at this time is, for example, 105 ° C. or more and 700 ° C. or less.
  • the composite hydroxide particles may be converted into composite oxide particles by the heating.
  • the composite hydroxide particles and / or composite oxide particles may be mixed with a lithium compound.
  • the lithium mixture is calcined in an oxidizing atmosphere at a temperature of 800 ° C. or higher and 1000 ° C. or lower for 5 hours or longer and 20 hours or shorter, and is composed of secondary particles 3 in which a plurality of primary particles 2 are aggregated.
  • Metal composite oxide particles (raw material) are obtained (step S30).
  • the firing temperature of the lithium mixture is 800 ° C. or higher and 1000 ° C. or lower.
  • the firing temperature is less than 800 ° C.
  • the reaction between the composite hydroxide particles and the lithium compound does not proceed sufficiently, the diffusion of lithium into the composite hydroxide particles is not sufficient, and excess lithium or unreacted
  • the composite oxide particles may remain, or the crystal structure may not be sufficiently formed in the primary particles, resulting in a decrease in output characteristics and battery capacity of the secondary battery.
  • the firing temperature exceeds 1000 ° C., intense sintering occurs between the secondary particles (raw materials), and abnormal grain growth occurs, so that the particles become coarse, and output characteristics and battery capacity may be reduced.
  • the holding time at the above firing temperature is 5 hours or more and 20 hours or less, preferably 5 hours or more and 10 hours or less.
  • secondary particles (raw materials) made of lithium nickel cobalt manganese composite oxide are not sufficiently generated.
  • the retention time exceeds 20 hours, intense sintering occurs between secondary particles (raw materials), abnormal grain growth may occur, and the particles may become coarse.
  • the atmosphere during firing may be an oxidizing atmosphere, but the oxygen concentration is preferably 18% by volume or more and 100% by volume or less. That is, the firing step (step S30) is preferably performed in the atmosphere to an oxygen stream, and more preferably in an air stream from the viewpoint of cost. When the oxygen concentration is less than 18% by volume, the oxidation may not be sufficient and the crystallinity of the lithium metal composite oxide particles may not be sufficient.
  • the furnace used for firing is not particularly limited as long as it can be heated in the atmosphere to an oxygen stream, but an electric furnace that does not generate gas is preferable, and a batch type or continuous type furnace is used.
  • the firing step (step S30) may further include a step of crushing the obtained lithium metal composite oxide particles (raw material). Under the above firing conditions, severe sintering and abnormal grain growth of the obtained lithium metal composite oxide particles (raw material) are suppressed, but slight sintering may occur between the lithium metal composite oxide particles (raw material). is there. Therefore, by crushing the fired lithium metal composite oxide particles (raw material), the slightly aggregated (sintered) secondary particles 3 can be separated. The crushing may be performed by a usual method, and may be performed to such an extent that the secondary particles 3 of the lithium metal composite oxide particles are not destroyed.
  • the lithium composite oxide particles (raw material) and the boron raw material are mixed to obtain a boron mixture (step S40). At least a part of the boron raw material reacts with lithium in the lithium metal composite oxide particles (raw material) in the subsequent heat treatment step (step S40) to form a lithium boron compound on the surface of the primary particles 2.
  • the boron raw material may be mixed in an amount corresponding to the boron content of the target positive electrode active material 10, for example, the number of atoms of Ni, Co, Mn in the lithium metal composite oxide particles (raw material) On the other hand, it is contained in the range of 2 at% or more and 4 at% or less. That is, in the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + ⁇ , the range of t indicating the content of boron (B) is 0.02 ⁇ t ⁇ 0.04.
  • the boron raw material By mixing the boron raw material in this manner, it is possible to achieve both improvement in output characteristics and suppression of gelation of the positive electrode mixture paste. Further, when the boron raw material is mixed so that t exceeds 0.04, the amount of boron dissolved in the crystal of the lithium composite oxide particles becomes excessive, and the battery characteristics may be deteriorated.
  • the boron raw material to be used is not particularly limited as long as it is a raw material containing boron, but from the viewpoint of controlling the increase in the amount of excess lithium and further suppressing gelation of the paste, use a boron raw material that does not contain lithium. Is preferred.
  • a boron raw material for example, a compound containing boron and oxygen can be used, and from the viewpoint of easy handling and excellent quality stability, it is preferable to use boron oxide, boron oxo acid and a mixture thereof. It is preferable to use orthoboric acid, and it is more preferable to use orthoboric acid.
  • a general mixer For mixing the lithium composite oxide particles (raw material) and the boron raw material, a general mixer can be used. For example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used. . The mixing may be performed by sufficiently mixing the lithium composite oxide particles (raw material) and the boron raw material to such an extent that the shape of the lithium composite oxide particles is not destroyed. Further, in the firing step (step S40), in order to uniformly contain boron among the lithium composite oxide particles (raw material), so that the lithium composite oxide particles and the boron raw material are uniformly dispersed in the boron mixture, It is preferable to mix thoroughly.
  • the boron mixture is heat-treated at a temperature of 200 ° C. or higher and 300 ° C. or lower in an air atmosphere to obtain the lithium metal composite oxide 1 (step S50).
  • the heat treatment is performed in the above temperature range, the boron raw material is reacted with the unreacted lithium compound present on the surface of the primary particles of the lithium metal composite oxide particles (raw material) or excessive lithium in the crystals of the primary particles.
  • boron is diffused into the secondary particles 3, and the lithium boron compound 4 is formed on the surface of the primary particles.
  • the positive electrode active material 10 using the obtained lithium metal composite oxide 1 can reduce the positive electrode resistance of the secondary battery and suppress gelation of the positive electrode mixture paste.
  • boron not only reacts with unreacted lithium (surplus lithium) on the surface of the primary particles, but also reacts excessively with lithium in the crystals of the primary particles, so that lithium in the primary particles This is considered to be because the lithium ions contributing to charge / discharge are reduced, and the amount of water-soluble Li contributing to the gelation of the positive electrode mixture paste on the surface of the primary particles is increased.
  • the heat treatment is performed in the above temperature range, and the amount of water-soluble Li present on the surface (whole) of the primary particles 2 is 1.3 times or less after the heat treatment with respect to that before the heat treatment.
  • the heat treatment is performed by adjusting the heat treatment conditions.
  • the amount of the water-soluble Li is in the above range, excessive extraction of lithium in the primary particle crystals is suppressed, and the crystallinity of the lithium composite oxide particles can be maintained.
  • generation of a lithium boron compound can be suppressed and the gelatinization of a positive mix paste can be suppressed.
  • the amount of water-soluble Li exceeds the above range, lithium in the lithium composite oxide particles is excessively extracted to form a lithium boron compound, thereby increasing the amount of detected excess lithium.
  • the amount of water-soluble Li can be controlled, for example, by adjusting the heat treatment time in accordance with the amount of boron raw material added.
  • the lower limit of the amount of water-soluble Li after the heat treatment is 1 time or more and preferably 1.3 times or less that before the heat treatment.
  • the increase amount of the water-soluble Li amount after heat treatment reflects the amount of the lithium boron compound 4 formed on the surface of the primary particle 2 as described above.
  • the heat treatment time can be appropriately adjusted according to the amount of surplus lithium formed, but is preferably 5 hours or more and 20 hours or less, more preferably 5 hours or more and 10 hours or less.
  • heat processing time is the said range, the lithium boron compound 4 can fully be produced
  • the heat treatment time is less than 5 hours, the lithium boron compound may not be sufficiently generated.
  • the heat treatment time exceeds 20 hours, lithium in the crystal of the lithium composite oxide particles may be excessively extracted.
  • the atmosphere during the heat treatment may be an oxidizing atmosphere, but the oxygen concentration is preferably 18% by volume or more and 100% by volume or less. That is, the heat treatment step (step S50) is preferably performed in the atmosphere to an oxygen stream, and more preferably in an air stream from the viewpoint of cost. When the oxygen concentration is less than 18% by volume, the formation of the lithium boron compound may not be sufficient.
  • the furnace similar to the furnace used by the said baking process can be used for the furnace used for heat processing.
  • Non-aqueous electrolyte secondary battery (hereinafter, also referred to as “secondary battery”) of the present embodiment uses the positive electrode active material described above as a positive electrode, thereby improving output characteristics and battery amount. In addition, it is possible to achieve both suppression of gelation of the positive electrode mixture paste when producing a secondary battery.
  • secondary battery of this embodiment can be comprised from the component similar to a well-known lithium ion secondary battery, for example, contains a positive electrode, a negative electrode, and a non-aqueous electrolyte.
  • nonaqueous electrolyte secondary battery may be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiment. it can.
  • the use of the secondary battery of this embodiment is not particularly limited.
  • a positive electrode of a secondary battery is manufactured using the positive electrode active material.
  • the positive electrode active material binder
  • activated carbon or a solvent is added and kneaded to prepare a positive electrode mixture paste.
  • the mixing ratio of each material in the positive electrode mixture is an element that determines the performance of the lithium secondary battery, it can be adjusted according to the application.
  • the mixing ratio of the materials can be the same as that of the positive electrode of a known lithium secondary battery.
  • the positive electrode active material is 60%. Up to 95% by mass, 1 to 20% by mass of a conductive material, and 1 to 20% by mass of a binder can be contained.
  • the conductive material for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), carbon black materials such as acetylene black and ketjen black, and the like can be used.
  • binder As the binder (binder), it plays the role of holding the active material particles.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • fluoro rubber ethylene propylene diene rubber
  • styrene butadiene cellulose series Resins
  • polyacrylic acid can be used.
  • the activated carbon paste can be added to the positive electrode mixture paste as necessary.
  • a positive electrode mixture paste can be obtained by dispersing a positive electrode active material, a conductive material, and activated carbon, and adding a solvent that dissolves the binder to the positive electrode mixture.
  • the electric double layer capacity can be increased by adding activated carbon to the positive electrode mixture.
  • the solvent can dissolve the fixing agent and adjust the viscosity and the like of the positive electrode mixture paste.
  • an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used as the solvent.
  • the obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, an aluminum foil, and dried to disperse the solvent, thereby producing a sheet-like positive electrode.
  • pressurization may be performed by a roll press or the like to increase the electrode density.
  • the sheet-like positive electrode thus obtained can be cut into an appropriate size according to the target battery and used for battery production.
  • the manufacturing method of a positive electrode is not restricted to the above-mentioned thing, You may use another manufacturing method.
  • the negative electrode metallic lithium, a lithium alloy, or the like can be used.
  • the negative electrode is prepared by mixing a negative electrode active material capable of occluding and desorbing lithium ions with a binder and adding a suitable solvent to form a paste on the surface of a metal foil current collector such as copper. You may use what was formed by compressing in order to apply
  • the negative electrode active material for example, a fired organic compound such as natural graphite, artificial graphite, and phenol resin, and a powdery carbon material such as coke can be used.
  • a fluorine-containing resin such as PVDF can be used as the negative electrode binder as in the positive electrode
  • an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder.
  • a solvent can be used.
  • a separator is interposed between the positive electrode and the negative electrode.
  • the separator separates the positive electrode and the negative electrode and holds the electrolyte, and a known one can be used.
  • a thin film such as polyethylene or polypropylene and a film having a large number of minute holes can be used. it can.
  • Non-aqueous electrolyte The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
  • organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, tetrahydrofuran, 2- Use one kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can do.
  • the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.
  • the non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte described above can have various shapes such as a cylindrical shape and a laminated shape.
  • the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the nonaqueous electrolyte secondary battery. .
  • the shape of the secondary battery of the present embodiment is not particularly limited, and can be various shapes such as a cylindrical shape and a stacked shape. Even if it takes any shape, a secondary battery can be comprised with the positive electrode mentioned above, a negative electrode, a separator, and nonaqueous electrolyte solution.
  • the manufacturing method of the secondary battery is not particularly limited, and for example, a positive electrode and a negative electrode are laminated through a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte solution, and a positive electrode current collector is obtained. And a positive electrode terminal that communicates with the outside and a negative electrode current collector and a negative electrode terminal that communicates with the outside using a current collecting lead or the like, and sealed in a battery case.
  • the secondary battery of this embodiment Since the secondary battery of this embodiment has a positive electrode using the positive electrode active material 10, it has a high capacity and excellent output characteristics. Moreover, since the positive electrode active material 10 used for a secondary battery can be obtained with an industrial manufacturing method, it is very excellent in productivity.
  • the use of the secondary battery of this embodiment is not particularly limited, for example, it can be suitably used as a power source for small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require high capacity.
  • the secondary battery of the present embodiment has higher thermal stability and safety when compared with a secondary battery using a positive electrode active material of a conventional lithium cobalt oxide or lithium nickel oxide as a positive electrode. In addition, it has a high capacity and excellent output characteristics. Therefore, the secondary battery using the positive electrode active material 10 can be reduced in size and output, and can be suitably used as, for example, a power source for an electric vehicle that is restricted by a mounting space.
  • the secondary battery of the present embodiment is used not only as a power source for an electric vehicle driven purely by electric energy but also as a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. be able to.
  • Composition analysis Measured by ICP emission spectrometry.
  • Average particle size and [(d90-d10) / average particle size] The average particle size of the positive electrode active material and [(d90-d10) / average particle size] were measured with a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac HRA).
  • the volume average particle diameter MV was used as the average particle diameter MV was used.
  • the average particle size of the primary particles is a scanning type of a cross-section of secondary particles (arbitrarily 20 particles selected) that are 80% or more of the volume average particle size MV measured using a laser light diffraction / scattering particle size analyzer.
  • reaction resistance The value of (reaction resistance) was calculated.
  • Measurement of water-soluble Li content The amount of water-soluble Li present on the surface of the primary particles of the obtained positive electrode active material was evaluated by neutralizing and titrating the amount of Li eluted from the positive electrode active material. After adding pure water to the obtained positive electrode active material and stirring for a certain time, it was measured by adding hydrochloric acid while measuring the pH of the filtered filtrate, and the amount of water-soluble Li was calculated from the amount of added hydrochloric acid. .
  • Viscosity stability of positive electrode composite paste 25.0 g of positive electrode active material, 1.5 g of carbon powder of conductive material, 2.9 g of polyvinylidene fluoride (PVDF), N-methyl-2-pyrrolidone (NMP) Were mixed with a planetary motion kneader to obtain a positive electrode mixture paste. The amount of N-methyl-2pyrrolidone (NMP) added was adjusted so that the viscosity would be 1.5 to 2.5 Pa ⁇ s by a viscosity measurement method using a vibration viscometer specified in JIS Z 8803: 2011. The obtained paste was stored for 76 hours, and the occurrence of gelation was visually evaluated.
  • PVDF polyvinylidene fluoride
  • NMP N-methyl-2-pyrrolidone
  • Example 1 (Crystallization process) First, the water in the reaction tank (60 L) was half-filled and stirred in the air atmosphere, while the temperature in the tank was set to 40 ° C., and 25 mass% sodium hydroxide aqueous solution and 25 mass% aqueous ammonia were added there. was added in an appropriate amount to adjust the pH value of the liquid in the tank to 12.8 based on the liquid temperature of 25 ° C. and the ammonia concentration in the liquid to 10 g / L.
  • TURBULA Type T2C manufactured by Willy et Bacofen
  • the mixture was sufficiently mixed using a mixer device (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a boron mixture.
  • the boron mixture was heat-treated in an air stream (oxygen: 21% by volume) for 10 hours at 250 ° C. to obtain a positive electrode active material.
  • Table 1 shows the average particle diameter, [(d90-d10) / average particle diameter] value, average particle diameter of primary particles, measurement results of water-soluble Li, and the like of the obtained positive electrode active material.
  • FIG. 3 shows the results of observation of the positive electrode active material using a scanning electron microscope (SEM: JSM-6360LA, manufactured by JEOL Ltd.). When the obtained positive electrode active material was analyzed with XPS (manufactured by ULVAC-PHI, VersaProbe II), a waveform indicating a combination with lithium was confirmed at the boron peak, and a lithium boron compound was present on the surface of the primary particles. Was confirmed.
  • FIG. 1 shows the average particle diameter, [(d90-d10) / average particle diameter] value, average particle diameter of primary particles, measurement results of water-soluble Li, and the like of the obtained positive electrode active material.
  • FIG. 3 shows the results of observation of the positive electrode active material using a scanning electron microscope (SEM: JSM-6360LA, manufactured by JEOL Ltd
  • FIG. 4 shows an example of the result of analyzing the presence of boron in the secondary particles by a soft X-ray emission spectroscopy (SXES) attached to the FE-SEM.
  • SXES soft X-ray emission spectroscopy
  • the obtained positive electrode active material 52.5 mg, acetylene black 15 mg, and polytetrafluoroethylene resin (PTFE) 7.5 mg were mixed and press-molded to a diameter of 11 mm and a thickness of 100 ⁇ m at a pressure of 100 MPa.
  • Evaluation electrode PE was prepared.
  • the produced positive electrode PE was dried at 120 ° C. for 12 hours in a vacuum dryer, and then a 2032 type coin battery CBA was produced using this positive electrode PE in an Ar atmosphere glove box in which the dew point was controlled at ⁇ 80 ° C.
  • Lithium (Li) metal having a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode NE, and the electrolyte solution is an equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO 4 as a supporting electrolyte ( Toyama Pharmaceutical Co., Ltd.) was used.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • 1M LiClO 4 1M LiClO 4 as a supporting electrolyte
  • separator SE a polyethylene porous film having a film thickness of 25 ⁇ m was used.
  • the coin battery had a gasket GA and a wave washer WW, and was assembled into a coin-type battery with the positive electrode can PC and the negative electrode can NC.
  • Table 2 shows the measurement results of the initial charge / discharge capacity and the positive electrode resistance value of the obtained positive electrode active material.
  • Example 2 A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 210 ° C. The evaluation results are shown in Tables 1 and 2.
  • Example 3 A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 290 ° C. The evaluation results are shown in Tables 1 and 2.
  • Example 1 A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that boric acid was not added. The evaluation results are shown in Tables 1 and 2.
  • Example 2 A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 150 ° C. The evaluation results are shown in Tables 1 and 2. When the obtained positive electrode active material was analyzed by XPS (manufactured by ULVAC-PHI, VersaProbe II), a waveform indicating a combination with lithium was not confirmed at the boron peak. From this result, it is considered that a boric acid compound containing lithium is not formed.
  • Example 3 A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 350 ° C. The evaluation results are shown in Tables 1 and 2.
  • FIG. 5 shows initial discharge capacities (A), positive electrode resistances (B) and aqueous solutions of Examples 1, 4, 5 and Comparative Examples 1, 4, 5 produced under the same conditions except for the addition amount of the boron raw material. It is the graph shown about the evaluation / measurement result of the property Li amount (C).
  • the amount of boron added is small (Comparative Examples 1 and 2), the positive electrode resistance is reduced little and gelation of the slurry occurs.
  • the amount of boron added is too large (Comparative Example 5) although the positive electrode resistance is reduced, the amount of water-soluble lithium increases and gelation of the slurry occurs.
  • extracting of lithium from lithium nickel cobalt manganese complex oxide increases, Li seat occupation rate falls and initial stage discharge capacity falls.
  • the positive electrode active material (heat treatment temperature: 150 ° C.) obtained in Comparative Example 2 no lithium boron compound was confirmed on the primary particles on the surface of the secondary particles, and the gelation of the slurry occurred. Moreover, the positive electrode active material (heat treatment temperature: 350 ° C.) obtained in Comparative Example 3 shows an increase in the amount of water-soluble Li and gelation of the paste. Furthermore, since the heat treatment temperature is high, lithium extraction from the lithium nickel cobalt manganese composite oxide is increased, the Li seat occupancy is lowered, and the initial discharge capacity is lowered.
  • the positive electrode active material of the present embodiment has good output characteristics, high battery capacity, and gelation of the paste at the time of electrode preparation by setting the heat treatment temperature and the amount of boron raw material to an appropriate range. It can be seen that an active material that is compatible with suppression can be obtained.
  • non-aqueous secondary battery using the positive electrode active material of the present embodiment exhibits excellent electrical characteristics such as high output and high battery capacity, portable electronic devices such as mobile phones and notebook computers, power tools, etc. Can be suitably used as a small-sized secondary battery mounted on the battery.

Abstract

Provided are: a positive electrode active material which enables the achievement of high output characteristics and high battery capacity if used for a positive electrode of a nonaqueous electrolyte secondary battery, and which is capable of suppressing gelation of a positive electrode mixture paste; and a method for producing this positive electrode active material. A positive electrode active material for nonaqueous electrolyte secondary batteries, which contains a lithium-nickel-cobalt-manganese composite oxide represented by general formula (1) Li1+sNixCoyMnzBtM1uO2+β and having a hexagonal lamellar crystal structure, and wherein: the lithium-nickel-cobalt-manganese composite oxide contains secondary particles, in each of which a plurality of primary particles aggregate, and a lithium-containing boron compound that is present on at least a part of the surface of each primary particle; and the amount of water-soluble Li present on the surface of each primary particle is 0.1% by mass or less relative to the total amount of the positive electrode active material.

Description

非水系電解質二次電池用正極活物質とその製造方法、および該正極活物質を用いた非水系電解質二次電池Positive electrode active material for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery using the positive electrode active material
　本発明は、非水系電解質二次電池用正極活物質とその製造方法、および該正極活物質を用いた非水系電解質二次電池に関する。 The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the positive electrode active material.
　近年、携帯電話やノート型パソコンなどの携帯電子機器の普及に伴い、高いエネルギー密度を有する小型で軽量な非水系電解質二次電池の開発が強く望まれている。また、ハイブリット自動車を始めとする電気自動車用の電池として高出力の二次電池の開発が強く望まれている。特に電気自動車用の電池は、高温から極低温までの広い温度域で用いられるため、このような広い温度域における高出力が必要である。 In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high output secondary battery is strongly desired as a battery for electric vehicles including hybrid vehicles. In particular, a battery for an electric vehicle is used in a wide temperature range from a high temperature to a very low temperature, and thus requires a high output in such a wide temperature range.
　このような要求を満たす二次電池として、リチウムイオン二次電池などの非水系電解質二次電池がある。非水系電解質二次電池は、負極および正極と電解液等で構成され、負極および正極の活物質として、リチウムを脱離および挿入することが可能な材料が用いられている。 There are non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries as secondary batteries that satisfy such requirements. A non-aqueous electrolyte secondary battery includes a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material of the negative electrode and the positive electrode.
　非水系電解質二次電池については、現在研究開発が盛んに行われているところであるが、中でも、層状またはスピネル型のリチウム金属複合酸化物を正極材料に用いた非水系電解質二次電池は、４Ｖ級の高い電圧が得られるため、高いエネルギー密度を有する電池として実用化が進んでいる。 Currently, research and development of non-aqueous electrolyte secondary batteries are being actively conducted. Among them, non-aqueous electrolyte secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are 4V. Since a high voltage can be obtained, it has been put to practical use as a battery having a high energy density.
　かかる非水系電解質二次電池の正極材料として、現在、合成が比較的容易なリチウムコバルト複合酸化物（ＬｉＣｏＯ２）や、コバルトよりも安価なニッケルを用いたリチウムニッケル複合酸化物（ＬｉＮｉＯ２）、リチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２）、マンガンを用いたリチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）、リチウムニッケルマンガン複合酸化物（ＬｉＮｉ０．５Ｍｎ０．５Ｏ２）などのリチウム複合酸化物が提案されている。 As a positive electrode material for such a non-aqueous electrolyte secondary battery, currently, lithium cobalt composite oxide (LiCoO 2 ) that is relatively easy to synthesize, lithium nickel composite oxide (LiNiO 2 ) using nickel that is cheaper than cobalt, Lithium nickel cobalt manganese composite oxide (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), lithium manganese composite oxide (LiMn 2 O 4 ) using manganese, lithium nickel manganese composite oxide (LiNi 0. 5 Mn 0.5 O 2) lithium composite oxide such as have been proposed.
　上記正極材料中でも、近年、熱安定性に優れて高容量であるリチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉ０．３３Ｃｏ０．３３Ｍｎ０．３３Ｏ２）が注目されている。リチウムニッケルコバルトマンガン複合酸化物は、リチウムコバルト複合酸化物やリチウムニッケル複合酸化物などと同じく層状化合物であり、遷移金属サイトにおいてニッケルとコバルト、マンガンを基本的に組成比１：１：１の割合で含んでいる。 Among the positive electrode materials, in recent years, lithium nickel cobalt manganese composite oxide (LiNi 0.33 Co 0.33 Mn 0.33 O 2 ) having excellent thermal stability and high capacity has attracted attention. Lithium nickel cobalt manganese composite oxide is a layered compound similar to lithium cobalt composite oxide and lithium nickel composite oxide, and basically has a composition ratio of 1: 1: 1 at the transition metal site between nickel, cobalt and manganese. Including.
　ところで、コバルトの比率が小さくなると、出力特性が低下する傾向にあり、リチウムニッケルコバルトマンガン複合酸化物（ＬｉＮｉ０．３３Ｃｏ０．３３Ｍｎ０．３３Ｏ２）は、リチウムコバルト複合酸化物（ＬｉＣｏＯ２）と比較し、抵抗が高く、高出力を得にくいという問題があった。これまで、リチウムニッケルコバルトマンガン複合酸化物にホウ素などを含む化合物を添加することによって、電池特性を改善させることがいくつか提案されている。 By the way, when the ratio of cobalt is reduced, the output characteristics tend to be reduced. Lithium nickel cobalt manganese composite oxide (LiNi 0.33 Co 0.33 Mn 0.33 O 2 ) is a lithium cobalt composite oxide (LiCoO). As compared with 2 ), there is a problem that resistance is high and high output is difficult to obtain. Heretofore, several proposals have been made to improve battery characteristics by adding a compound containing boron or the like to lithium nickel cobalt manganese composite oxide.
　例えば、特許文献１には、少なくとも層状構造のリチウム遷移金属複合酸化物を有する非水電解質二次電池用正極活物質であって、前記リチウム遷移金属複合酸化物は、一次粒子およびその凝集体である二次粒子の一方または両方からなる粒子の形態で存在し、前記一次粒子のアスペクト比が１～１．８であり、前記粒子の少なくとも表面に、モリブデン、バナジウム、タングステン、ホウ素およびフッ素からなる群から選ばれる少なくとも１種を有する化合物を有する非水電解質二次電池用正極活物質が提案されている。粒子の表面にモリブデン、バナジウム、タングステン、ホウ素およびフッ素からなる群から選ばれる少なくとも１種を有する化合物を有することにより、導電性が向上するとされている。 For example, Patent Document 1 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide, wherein the lithium transition metal composite oxide includes primary particles and aggregates thereof. It exists in the form of particles comprising one or both of secondary particles, the primary particles have an aspect ratio of 1 to 1.8, and at least the surface of the particles is composed of molybdenum, vanadium, tungsten, boron, and fluorine. A positive electrode active material for a non-aqueous electrolyte secondary battery having a compound having at least one selected from the group has been proposed. By having a compound having at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on the surface of the particles, the conductivity is improved.
　特許文献２には、リチウムイオンの挿入・脱離が可能な機能を有するリチウム遷移金属系化合物を主成分とし、該主成分原料に、Ｂ及びＢｉから選ばれる少なくとも１種の元素を含有する化合物と、Ｍｏ、Ｗ、Ｎｂ、Ｔａ及びＲｅから選ばれる少なくとも１種の元素を含有する化合物をそれぞれ１種併用添加した後、焼成されてなるリチウム二次電池正極材料用リチウム遷移金属系化合物粉体が提案されている。添加元素を併用添加した後、焼成することにより、粒成長及び焼結の抑えられた微細な粒子からなるリチウム遷移金属系化合物粉体が得られ、レートや出力特性が改善されるとともに、取り扱いや電極調製の容易なリチウム含有遷移金属系化合物粉体を得ることができるとしている。 Patent Document 2 discloses a compound containing, as a main component, a lithium transition metal compound having a function capable of inserting and removing lithium ions, and containing at least one element selected from B and Bi as the main component material And a lithium transition metal-based compound powder for a lithium secondary battery positive electrode material, which is fired after adding a compound containing at least one element selected from Mo, W, Nb, Ta and Re Has been proposed. After adding the additive element in combination, firing is performed to obtain a lithium transition metal-based compound powder composed of fine particles with suppressed grain growth and sintering, and the rate and output characteristics are improved. It is said that a lithium-containing transition metal compound powder that is easy to prepare an electrode can be obtained.
　特許文献３には、一般式ＬｉａＮｉ１－ｘ－ｙＣｏｘＭ１ ｙＷｚＭ２ ｗＯ２（１．０≦ａ≦１．５、０≦ｘ≦０．５、０≦ｙ≦０．５、０．００２≦ｚ≦０．０３、０≦ｗ≦０．０２、０≦ｘ＋ｙ≦０．７、Ｍ１はＭｎ及びＡｌからなる群より選択される少なくとも一種、Ｍ２はＺｒ、Ｔｉ、Ｍｇ、Ｔａ、Ｎｂ及びＭｏからなる群より選択される少なくとも一種）で表されるリチウム遷移金属複合酸化物と、少なくともホウ素元素及び酸素元素を含むホウ素化合物とを含む非水電解液二次電池用正極組成物が提案されている。ニッケル及びタングステンを必須とするリチウム遷移金属複合酸化物と、特定のホウ素化合物とを含む正極組成物を用いることにより、リチウム遷移金属複合酸化物を用いた正極組成物において出力特性及びサイクル特性を向上させることができるとしている。 Patent Document 3 discloses a general formula Li a Ni 1-xy Co x M 1 y W z M 2 w O 2 (1.0 ≦ a ≦ 1.5, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.5, 0.002 ≦ z ≦ 0.03, 0 ≦ w ≦ 0.02, 0 ≦ x + y ≦ 0.7, M 1 is at least one selected from the group consisting of Mn and Al, M 2 is A non-aqueous electrolyte comprising a lithium transition metal composite oxide represented by at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb, and Mo) and a boron compound containing at least a boron element and an oxygen element A positive electrode composition for a secondary battery has been proposed. By using a positive electrode composition containing a lithium transition metal composite oxide containing nickel and tungsten and a specific boron compound, the output characteristics and cycle characteristics of the positive electrode composition using the lithium transition metal composite oxide are improved. It can be made to.
　特許文献４には、少なくとも層状の結晶構造のリチウム遷移金属複合酸化物を有する非水電解液二次電池用正極活物質であって、前記リチウム遷移金属複合酸化物は、粒子であるとともに、少なくとも前記粒子の表面にホウ酸リチウムを有する、非水電解液二次電池用正極活物質が提案されている。粒子の表面にホウ酸リチウムを有することにより、初期放電容量および初期効率を同等に維持しつつ、熱安定性を向上させることができるとしている。 Patent Document 4 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered crystal structure lithium transition metal composite oxide, wherein the lithium transition metal composite oxide is a particle, and at least A positive electrode active material for a non-aqueous electrolyte secondary battery having lithium borate on the surface of the particles has been proposed. By having lithium borate on the surface of the particles, it is possible to improve the thermal stability while maintaining the same initial discharge capacity and initial efficiency.
　特許文献５には、リチウム（Ｌｉ）と、ニッケル（Ｎｉ）およびコバルト（Ｃｏ）のうちの少なくとも一方とを含む複合酸化物粒子に、硫酸塩およびホウ酸化合物のうちの少なくとも一方を被着する工程と、上記硫酸塩およびホウ酸化合物のうちの少なくとも一方の被着した上記複合酸化物粒子を酸化性雰囲気下で加熱処理する工程と、を有することを特徴とする正極活物質の製造方法が提案されている。この提案によれば、二次電池の高容量化と、充放電効率の向上とを実現することが可能な正極活物質を製造することができるとしている。 In Patent Document 5, at least one of a sulfate and a boric acid compound is deposited on a composite oxide particle containing lithium (Li) and at least one of nickel (Ni) and cobalt (Co). And a step of heat-treating the composite oxide particles deposited on at least one of the sulfate and boric acid compounds in an oxidizing atmosphere. Proposed. According to this proposal, it is said that a positive electrode active material capable of realizing an increase in capacity of a secondary battery and an improvement in charge / discharge efficiency can be manufactured.
　特許文献６には、ＬｉａＮｉｘＣｏｙＡｌｚＯ２（但し、Ｎｉは、Ｎｉ全体の量を１としたときに、Ｎｉの０．１以下の範囲内で、Ｍｎ、Ｃｒ、Ｆｅ、Ｖ、Ｍｇ、Ｔｉ、Ｚｒ、Ｎｂ、Ｍｏ、Ｗ、Ｃｕ、Ｚｎ、Ｇａ、Ｉｎ、Ｓｎ、Ｌａ、Ｃｅからなる群から選択される１種または２種以上の金属元素と置換可能である。また、式中ａ、ｘ、ｙ、ｚは、０．３≦ａ≦１．０５、０．６０＜ｘ＜０．９０、０．１０＜ｙ＜０．４０、０．０１＜ｚ＜０．２０の範囲内の値であり、ｘ、ｙおよびｚの間にはｘ＋ｙ＋ｚ＝１の関係がある。）で平均組成が表される複合酸化物粒子にホウ酸化合物を被着させて加熱処理を行ったもので、炭酸イオンの含有量が０．１５重量％以下であり、かつホウ酸イオンの含有量が０．０１重量％以上５．０重量％以下である正極活物質が提案されている。ホウ酸化合物を被着させることにより、複合酸化物粒子に含まれる炭酸根とホウ酸化合物とが置換され、二次電池の電池内部におけるガス発生量を低減させることができるとしている。 Patent Document 6 discloses Li a Ni x Co y Al z O 2 (where Ni is Mn, Cr, Fe, It can be substituted with one or more metal elements selected from the group consisting of V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. In the formula, a, x, y, and z are 0.3 ≦ a ≦ 1.05, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0. The value is within the range of 20, and there is a relationship of x + y + z = 1 between x, y, and z.) The boric acid compound is deposited on the composite oxide particles whose average composition is expressed by the following formula: The carbonate ion content is 0.15 wt% or less, and the borate ion content is 0.01 wt% or more and 5.0 wt%. % Positive electrode active material is proposed. By depositing the boric acid compound, the carbonate radical and boric acid compound contained in the composite oxide particles are replaced, and the amount of gas generated inside the battery of the secondary battery can be reduced.
　一方、均一で適度な粒径を有し、かつ中空構造の粒子によって構成される正極を用いることで、電池として高い性能（高サイクル特性、低抵抗、高出力）を得る技術も提案されている。 On the other hand, a technique for obtaining high performance (high cycle characteristics, low resistance, high output) as a battery by using a positive electrode having a uniform and appropriate particle size and comprising hollow particles has also been proposed. .
　例えば、特許文献７には、一般式：Ｌｉ１＋ｕＮｉｘＭｎｙＣｏｚＭｔＯ２（－０．０５≦ｕ≦０．５０、ｘ＋ｙ＋ｚ＋ｔ＝１、０．３≦ｘ≦０．７、０．１≦ｙ≦０．５５、０≦ｚ≦０．４、０≦ｔ≦０．１、Ｍは添加元素であり、Ｍｇ、Ｃａ、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｚｒ、Ｎｂ、Ｍｏ、Ｗから選択される１種以上の元素）で表され、層状構造を有する六方晶系リチウム含有複合酸化物により構成されるリチウムニッケルマンガン複合酸化物からなる正極活物質であって、平均粒径が２～８μｍであり、粒度分布の広がりを示す指標である〔（ｄ９０－ｄ１０）／平均粒径〕が０．６０以下であり、凝集した一次粒子が焼結している外殻部と、その内側に存在する中空部とからなる中空構造を備えることを特徴とする非水系電解質二次電池用正極活物質が提案されている。この正極活物質は、非水系二次電池に用いた場合に高容量でサイクル特性が良好で、高出力を可能とするとされている。 For example, Patent Document 7 discloses a general formula: Li 1 + u Ni x Mn y Co z M t O 2 (−0.05 ≦ u ≦ 0.50, x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is an additive element, and Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, A positive electrode active material comprising a lithium nickel manganese composite oxide composed of a hexagonal lithium-containing composite oxide having a layered structure and having an average particle diameter of at least one element selected from W) 2 to 8 μm, and the index indicating the spread of the particle size distribution [(d90−d10) / average particle size] is 0.60 or less, and the outer shell portion in which the aggregated primary particles are sintered, Non-aqueous electrolysis characterized by having a hollow structure composed of a hollow portion present inside The positive electrode active material has been proposed for a secondary battery. This positive electrode active material is said to have a high capacity, good cycle characteristics, and high output when used in a non-aqueous secondary battery.
特開２００５－２５１７１６号公報JP 2005-251716 A 特開２０１１－１０８５５４号公報JP 2011-108554 A 特開２０１３－２３９４３４号公報JP 2013-239434 A 特開２００４－３３５２７８号公報JP 2004-335278 A 特開２００９－１４６７３９号公報JP 2009-146739 A 特開２０１０－０４０３８２号公報JP 2010-040382 A 国際公開第２０１２／１３１８８１号International Publication No. 2012/131881
　上記提案は、いずれも出力特性などの電池特性が改善されるとされているが、ホウ素を添加することによって、電極作製時の正極合材ペーストのゲル化の問題が生じることがあり、出力特性や電池容量などの電池特性の改善とともに、ゲル化の改善が望まれている。 All of the above proposals are said to improve battery characteristics such as output characteristics, but adding boron may cause gelation problem of the positive electrode mixture paste at the time of electrode preparation. Improvement of gelation is desired along with improvement of battery characteristics such as battery capacity.
　本発明は、これら事情を鑑みてなされたものであり、非水系電解質二次電池に用いられた際の出力特性及び電池容量を向上させ、かつ、電極作製時の正極合材ペーストのゲル化を抑制した正極活物質を提供することを目的とするものである。また、本発明は、このような正極活物質を、工業規模の生産において容易に製造することができる方法を提供することを目的とする。 The present invention has been made in view of these circumstances, and improves the output characteristics and battery capacity when used in a non-aqueous electrolyte secondary battery, and the gelation of the positive electrode mixture paste during electrode production. It aims at providing the positive electrode active material which suppressed. Moreover, an object of this invention is to provide the method which can manufacture such a positive electrode active material easily in industrial scale production.
　本発明者は、上記課題を解決するため、鋭意検討を重ねた結果、特定量のホウ素化合物を、正極活物質を構成するリチウムニッケルコバルトマンガン複合酸化物の一次粒子表面に存在させるとともに、一次粒子表面に存在する水溶性Ｌｉ量を特定の範囲とすることで、この正極活物質を正極に用いた二次電池の出力特性及び電池容量の向上と、正極合材ペーストのゲル化の抑制とを両立させることが可能であると知見を得て、本発明を完成するに至った。 As a result of intensive studies in order to solve the above-mentioned problems, the present inventor causes a specific amount of a boron compound to be present on the primary particle surface of the lithium nickel cobalt manganese composite oxide constituting the positive electrode active material, and the primary particles. By making the amount of water-soluble Li present on the surface into a specific range, the output characteristics and battery capacity of a secondary battery using this positive electrode active material for the positive electrode are improved, and the gelation of the positive electrode mixture paste is suppressed. The knowledge that it is possible to achieve both has been obtained, and the present invention has been completed.
　本発明の第１の態様では、一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物を含む非水系電解質二次電池用正極活物質であって、リチウムニッケルコバルトマンガン複合酸化物は、複数の一次粒子が凝集した二次粒子と、一次粒子表面の少なくとも一部に存在するリチウムを含むホウ素化合物と、を含み、一次粒子表面に存在する水溶性Ｌｉ量が、正極活物質全量に対して、０．１質量％以下である、非水系電解質二次電池用正極活物質が提供される。 In the first aspect of the present invention, the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (wherein, in the formula (1), M1 represents Li, Ni, Co, Mn, Elements other than B, −0.05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5), and having a hexagonal layered crystal structure A positive electrode active material for a non-aqueous electrolyte secondary battery containing a composite oxide, wherein the lithium nickel cobalt manganese composite oxide is present on secondary particles in which a plurality of primary particles are aggregated and at least a part of the surface of the primary particles A boron compound containing lithium, and the amount of water-soluble Li present on the primary particle surface is positive. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is 0.1% by mass or less based on the total amount of the polar active material, is provided.
　また、二次粒子の平均粒径が３μｍ以上２０μｍ以下であることが好ましい。また、一次粒子の平均粒径が０．２μｍ以上０．５μｍ以下であることが好ましい。また、二次粒子の粒度分布の広がりを示す指標である〔（ｄ９０－ｄ１０）／平均粒径〕が０．６０以下であることが好ましい。また、二次粒子が、その内部に中空部を形成した中空構造を有することが好ましい。 Moreover, it is preferable that the average particle diameter of the secondary particles is 3 μm or more and 20 μm or less. Moreover, it is preferable that the average particle diameter of a primary particle is 0.2 micrometer or more and 0.5 micrometer or less. Further, it is preferable that [(d90−d10) / average particle diameter], which is an index indicating the spread of the particle size distribution of the secondary particles, is 0.60 or less. The secondary particles preferably have a hollow structure in which a hollow portion is formed.
　本発明の第２の態様では、一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物からなる非水系電解質二次電池用正極活物質の製造方法であって、一般式（２）：ＮｉｘＣｏｙＭｎｚＭ２ｕ（ＯＨ）２＋α（前記式（２）中、Ｍ２は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ以外の元素であり、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０≦ｕ≦０．１、及び、０≦α≦０．５を満たす。）で表されるニッケルコバルトマンガン複合水酸化物粒子を晶析により得る晶析工程と、ニッケルコバルトマンガン複合水酸化物粒子に、リチウム以外の金属元素の原子数の合計に対するリチウムの原子数の比が０．９５以上１．２０以下となるように、リチウム化合物を混合してリチウム混合物を得るリチウム混合工程と、リチウム混合物を、酸化性雰囲気中において、８００℃以上１０００℃以下の温度で５時間以上２０時間以下保持して焼成することにより、複数の一次粒子が凝集した二次粒子からなるニッケルコバルトマンガン複合水酸化物粒子を得る焼成工程と、ニッケルコバルトマンガン複合水酸化物粒子とホウ素原料とを混合してホウ素混合物を得るホウ素混合工程と、ホウ素混合物を、酸化性雰囲気中において２００℃以上３００℃以下の温度で熱処理する熱処理工程と、を備え、熱処理工程において、前記一次粒子表面に存在する水溶性Ｌｉ量が、前記熱処理前に対して、前記熱処理後に１．３倍以下となるように熱処理を行う、非水系電解質二次電池用正極活物質の製造方法が提供される。 In the second aspect of the present invention, the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (wherein, in the formula (1), M1 represents Li, Ni, Co, Mn, Elements other than B, −0.05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5), and having a hexagonal layered crystal structure A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a composite oxide, wherein the general formula (2): Ni x Co y Mn z M2 u (OH) 2 + α (wherein M2 is the formula (2)) , Li, Ni, Co, Mn, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + Y + z + u = 1, 0 ≦ u ≦ 0.1 and 0 ≦ α ≦ 0.5)), and a crystallization process for obtaining nickel cobalt manganese composite hydroxide particles represented by crystallization, and nickel cobalt manganese Lithium mixing to obtain a lithium mixture by mixing lithium compounds with composite hydroxide particles so that the ratio of the number of lithium atoms to the total number of atoms of metal elements other than lithium is 0.95 or more and 1.20 or less And nickel cobalt comprising secondary particles in which a plurality of primary particles are aggregated by holding and baking the lithium mixture in an oxidizing atmosphere at a temperature of 800 ° C. to 1000 ° C. for 5 hours to 20 hours. A calcination step for obtaining manganese composite hydroxide particles, and boron for obtaining a boron mixture by mixing nickel cobalt manganese composite hydroxide particles and a boron raw material. A heat treatment step of heat-treating the boron mixture at a temperature of 200 ° C. or higher and 300 ° C. or lower in an oxidizing atmosphere. In the heat treatment step, the amount of water-soluble Li present on the surface of the primary particles is Provided is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, in which heat treatment is performed so that the heat treatment is 1.3 times or less after the heat treatment.
　また、ホウ素原料が、酸化ホウ素およびホウ素のオキソ酸の少なくとも一つであることが好ましい。また、ホウ素原料が、オルトホウ酸であることが好ましい。また、焼成工程で得られたリチウムニッケルコバルトマンガン複合酸化物粒子を解砕する解砕工程をさらに備えてもよい。 Further, it is preferable that the boron raw material is at least one of boron oxide and boron oxo acid. Moreover, it is preferable that a boron raw material is orthoboric acid. Moreover, you may further provide the crushing process which crushes the lithium nickel cobalt manganese complex oxide particle obtained at the baking process.
　本発明の第３の態様では、正極と、負極と、セパレータと、非水系電解質とを備え、正極は、前記非水系電解質二次電池用正極活物質を含む非水電解質二次電池が提供される。 According to a third aspect of the present invention, there is provided a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein the positive electrode includes the positive electrode active material for the nonaqueous electrolyte secondary battery. The
　本発明の正極活物質は、非水電解質二次電池の正極に用いられた際に、優れた出力特性と高い電池容量が得られる。また、本発明の正極活物質は、電極作製の際、正極合材ペーストのゲル化を抑制でき、非水電解質二次電池の製造をより容易にすることができる。 When the positive electrode active material of the present invention is used for the positive electrode of a non-aqueous electrolyte secondary battery, excellent output characteristics and high battery capacity can be obtained. Moreover, the positive electrode active material of the present invention can suppress gelation of the positive electrode mixture paste during electrode production, and can facilitate the production of a non-aqueous electrolyte secondary battery.
　さらに、本発明の正極活物質の製造方法は、工業的規模の生産においても容易に実施することができ、工業的に極めて有用である。 Furthermore, the method for producing a positive electrode active material of the present invention can be easily implemented even in industrial scale production and is extremely useful industrially.
図１（Ａ）及び（Ｂ）は、本実施形態の正極活物質の一例を示した図である。1A and 1B are diagrams showing an example of the positive electrode active material of the present embodiment. 図２は、本実施形態の正極活物質の製造方法の一例を示した図である。FIG. 2 is a diagram illustrating an example of a method for producing a positive electrode active material according to the present embodiment. 図３は、本実施形態の正極活物質の走査型電子顕微鏡による観察結果の一例を示す写真（観察倍率１０００倍）である。FIG. 3 is a photograph (observation magnification 1000 times) showing an example of the observation result of the positive electrode active material of the present embodiment by a scanning electron microscope. 図４（Ａ）及び（Ｂ）は、本実施形態の正極活物質断面の軟Ｘ線発光分光による分析結果の一例を示す写真である。4 (A) and 4 (B) are photographs showing examples of the results of analysis by soft X-ray emission spectroscopy of the cross section of the positive electrode active material of the present embodiment. 図５（Ａ）～（Ｃ）は、実施例及び比較例で得られた正極活物質の評価結果を示すグラフである。5A to 5C are graphs showing the evaluation results of the positive electrode active materials obtained in Examples and Comparative Examples. 図６は、評価に用いたコイン電池の構造を示す概略図である。FIG. 6 is a schematic diagram showing the structure of the coin battery used for the evaluation. 図７は、ナイキストプロットの一例を示す図である。FIG. 7 is a diagram illustrating an example of a Nyquist plot. 図８は、インピーダンス評価に用いた等価回路を示す図である。FIG. 8 is a diagram showing an equivalent circuit used for impedance evaluation.
　　以下、図面を参照して、本実施形態の非水系電解質二次電池用正極活物質とその製造方法、及び、非水系電解質二次電池用正極活物質について説明する。なお、図面においては、各構成をわかりやすくするために、一部を強調して、あるいは一部を簡略化して表しており、実際の構造または形状、縮尺等が異なっている場合がある。 Hereinafter, with reference to the drawings, the positive electrode active material for a non-aqueous electrolyte secondary battery, the manufacturing method thereof, and the positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment will be described. In the drawings, in order to make each configuration easy to understand, some parts are emphasized or some parts are simplified, and actual structures, shapes, scales, and the like may be different.
１．非水系電解質二次電池用正極活物質
　図１は、本実施形態に係る非水系電解質二次電池用正極活物質１０（以下、「正極活物質１０」ともいう。）の一例を示す模式図である。図１に示すように、正極活物質１０は、リチウムニッケルコバルトマンガン複合酸化物１（以下、「リチウム金属複合酸化物１」ともいう。）を含む。 1. FIG. 1 is a schematic diagram showing an example of a positive electrode active material 10 for a non-aqueous electrolyte secondary battery (hereinafter also referred to as “positive electrode active material 10”) according to the present embodiment. is there. As shown in FIG. 1, the positive electrode active material 10 includes lithium nickel cobalt manganese composite oxide 1 (hereinafter also referred to as “lithium metal composite oxide 1”).
　リチウム複合金属酸化物１は、一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有する。また、リチウム複合金属酸化物１は、複数の一次粒子２が凝集した二次粒子３と、一次粒子２の表面の少なくとも一部に存在するリチウムを含むホウ素化合物４（以下、「リチウムホウ素化合物４」ともいう。）と、を含み、一次粒子２の表面に存在する水溶性Ｌｉ量が、正極活物質全量に対して、０．１質量％以下である。 The lithium composite metal oxide 1 has the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (in the formula (1), M1 is other than Li, Ni, Co, Mn, and B) -0.05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5.) And has a hexagonal layered crystal structure. The lithium composite metal oxide 1 includes a secondary particle 3 in which a plurality of primary particles 2 are aggregated, and a boron compound 4 containing lithium present on at least a part of the surface of the primary particle 2 (hereinafter referred to as “lithium boron compound 4”). The amount of water-soluble Li present on the surface of the primary particles 2 is 0.1% by mass or less based on the total amount of the positive electrode active material.
　正極活物質１０は、一次粒子２の表面にリチウムホウ素化合物４を存在させることによって、正極活物質１０を用いた非水系電解質二次電池（以下、「二次電池」ともいう。）において、正極の反応抵抗（以下、「正極抵抗」ともいう。）を低減させ、かつ、初期充電容量（以下、「電池容量」ともいう。）を向上させる。そして、二次電池の正極抵抗が低減されることで、二次電池内で損失される電圧が減少し、実際に負荷側に印加される電圧が相対的に高くなるため、高出力が得られる。また、負荷側への印加電圧が高くなることで、正極でのリチウムの挿抜が十分に行われるため、電池容量も向上されると考えられる。 The positive electrode active material 10 is a positive electrode in a non-aqueous electrolyte secondary battery (hereinafter also referred to as “secondary battery”) using the positive electrode active material 10 by allowing the lithium boron compound 4 to be present on the surfaces of the primary particles 2. The reaction resistance (hereinafter also referred to as “positive electrode resistance”) is reduced, and the initial charge capacity (hereinafter also referred to as “battery capacity”) is improved. And by reducing the positive electrode resistance of the secondary battery, the voltage lost in the secondary battery is reduced, and the voltage actually applied to the load side becomes relatively high, so a high output is obtained. . Moreover, since the voltage applied to the load side is increased, lithium is sufficiently inserted and extracted from the positive electrode, and thus the battery capacity is considered to be improved.
　正極活物質１０を用いた二次電池の正極抵抗が低下するメカニズムの詳細は不明であるが、一次粒子２表面に形成されるリチウムホウ素化合物４は、リチウムイオン伝導性が高く、リチウムイオンの移動を促す効果があるため、二次電池の正極において、電解液と正極活物質１０との界面でＬｉの伝導パスを形成し、正極抵抗を低減して、電池の出力特性及び電池容量を向上させると考えられる。リチウムホウ素化合物４は、例えば、リチウムホウ素複合酸化物の形態を有する。 Although the details of the mechanism by which the positive electrode resistance of the secondary battery using the positive electrode active material 10 decreases are unknown, the lithium boron compound 4 formed on the surface of the primary particles 2 has high lithium ion conductivity and the movement of lithium ions. Therefore, in the positive electrode of the secondary battery, a Li conduction path is formed at the interface between the electrolytic solution and the positive electrode active material 10 to reduce the positive electrode resistance, thereby improving the battery output characteristics and the battery capacity. it is conceivable that. The lithium boron compound 4 has a form of, for example, a lithium boron composite oxide.
　また、正極活物質１０は、一次粒子２の表面にリチウムホウ素化合物４が存在し、かつ、一次粒子２の表面に存在する水溶性Ｌｉ量が０．１質量％以下であることにより、この正極活物質１０を用いた正極合材ペースト（以下、「ペースト」ともいう。）のゲル化を抑制することができる。ここで、一次粒子２の表面に存在する水溶性Ｌｉ量とは、正極活物質１０を水に分散させた際、水に溶出するＬｉの量をいう。リチウムホウ素化合物４の少なくとも一部も、正極活物質１０を水に分散させた際、水に溶出するため、水溶性Ｌｉ量には、上述した一次粒子２の表面に存在する余剰リチウム化合物や、リチウムホウ素化合物４に由来するＬｉが含まれる。そして、本発明者らは、水溶性Ｌｉ量が上記範囲となるように、リチウムホウ素化合物４を一次粒子２の表面に形成することにより、ペーストのゲル化が抑制されることを見出した。 In addition, the positive electrode active material 10 has the lithium boron compound 4 on the surface of the primary particle 2 and the amount of water-soluble Li existing on the surface of the primary particle 2 is 0.1% by mass or less. Gelation of the positive electrode mixture paste (hereinafter also referred to as “paste”) using the active material 10 can be suppressed. Here, the amount of water-soluble Li existing on the surface of the primary particles 2 refers to the amount of Li eluted in water when the positive electrode active material 10 is dispersed in water. Since at least a part of the lithium boron compound 4 is also eluted in water when the positive electrode active material 10 is dispersed in water, the amount of water-soluble Li includes the excess lithium compound present on the surface of the primary particles 2 described above, Li derived from the lithium boron compound 4 is included. And the present inventors discovered that gelation of a paste was suppressed by forming the lithium boron compound 4 in the surface of the primary particle 2 so that water-soluble Li amount may become the said range.
　正極合材ペーストのゲル化は、リチウム複合金属酸化物の一次粒子の表面に存在する、水酸化リチウム、炭酸リチウムなどの余剰リチウム化合物が、正極合材ペースト中に含まれる水分中に溶出して、ペーストのｐＨ値を上昇させ、引き起こされると考えられている。正極活物質１０において、ペーストのゲル化が抑制されるメカニズムの詳細は不明であるが、リチウムホウ素化合物４の原料の一つであるホウ素原料が、正極活物質１０の製造工程において、リチウム金属複合酸化物粒子（原料）中の一次粒子表面に存在する余剰リチウム化合物と反応して、リチウムホウ素化合物４を形成することにより、ペーストのゲルが抑制されると考えられる。 The gelation of the positive electrode mixture paste is caused by excess lithium compounds such as lithium hydroxide and lithium carbonate that are present on the surface of the primary particles of the lithium composite metal oxide being eluted in the water contained in the positive electrode mixture paste. It is believed to be caused by raising the pH value of the paste. Although the details of the mechanism by which the gelation of the paste is suppressed in the positive electrode active material 10 are not known, a boron raw material that is one of the raw materials of the lithium boron compound 4 is a lithium metal composite in the manufacturing process of the positive electrode active material 10. It is considered that the gel of the paste is suppressed by reacting with an excess lithium compound present on the surface of the primary particles in the oxide particles (raw material) to form the lithium boron compound 4.
　一方、一次粒子２の表面の水溶性Ｌｉの量が、正極活物質１０全量に対して、０．１質量％を超える場合、ペーストのゲル化の抑制効果を得られない。この原因の詳細は不明であるが、一次粒子２の表面にリチウムホウ素化合物４が過剰に形成されて、ゲル化に寄与する水溶性リチウム化合物が増加するためと考えられる。なお、正極活物質１０の製造工程において、ホウ素原料は、リチウム金属複合酸化物粒子（原料）の一次粒子表面の余剰リチウム化合物と反応する以外にも、リチウム金属複合酸化物粒子（原料）の結晶内から引き抜かれたリチウムとも反応すると考えられる。よって、リチウムホウ素化合物４が過剰に形成された場合、充放電に寄与するリチウムイオンを減少させ、二次電池の電池容量の低下も引き起こす。 On the other hand, when the amount of water-soluble Li on the surface of the primary particle 2 exceeds 0.1% by mass with respect to the total amount of the positive electrode active material 10, an effect of suppressing gelation of the paste cannot be obtained. Although the details of the cause are unknown, it is considered that the lithium boron compound 4 is excessively formed on the surface of the primary particle 2 and the water-soluble lithium compound contributing to gelation increases. In addition, in the manufacturing process of the positive electrode active material 10, the boron raw material reacts with the surplus lithium compound on the surface of the primary particles of the lithium metal composite oxide particles (raw material), and the crystal of the lithium metal composite oxide particles (raw material). It is thought to react with lithium extracted from the inside. Therefore, when the lithium boron compound 4 is excessively formed, lithium ions contributing to charge / discharge are reduced, and the battery capacity of the secondary battery is also reduced.
　ここで、一次粒子２の表面とは、二次電池の正極において、電解液との接触が可能な一次粒子２の表面をいう。リチウムホウ素化合物４は、電解液との接触が可能な一次粒子２の表面に形成されることにより、正極抵抗を低減させ、出力特性及び電池容量を向上させることが可能となる。一次粒子２の表面は、例えば、図１（Ａ）に示すように、二次粒子３の外面（表面）に露出する一次粒子２ａの表面や、二次粒子３の表面と通じて電解液が浸透可能な二次粒子３内部の一次粒子２ｂの表面などを含む。また、一次粒子２の表面は、一次粒子２間の粒界であっても、一次粒子２の結合が不完全で電解液が浸透可能な状態であれば含む。また、一次粒子２の表面は、例えば、図１（Ｂ）に示すように、二次粒子３内部の中空部５（空隙）に露出している一次粒子２ｃの表面を含む。 Here, the surface of the primary particle 2 refers to the surface of the primary particle 2 that can be in contact with the electrolytic solution in the positive electrode of the secondary battery. The lithium boron compound 4 is formed on the surface of the primary particle 2 that can be in contact with the electrolytic solution, thereby reducing the positive electrode resistance and improving the output characteristics and the battery capacity. For example, as shown in FIG. 1A, the surface of the primary particle 2 has an electrolyte solution that communicates with the surface of the primary particle 2 a exposed on the outer surface (surface) of the secondary particle 3 or the surface of the secondary particle 3. The surface of the primary particle 2b inside the permeable secondary particle 3 is included. Further, the surface of the primary particle 2 includes the boundary between the primary particles 2 as long as the primary particles 2 are incompletely bonded and the electrolyte solution can permeate. Moreover, the surface of the primary particle 2 contains the surface of the primary particle 2c exposed to the hollow part 5 (space | gap) inside the secondary particle 3, for example, as shown in FIG.1 (B).
　二次粒子３の表面に露出する一次粒子２ａの表面のリチウムホウ素化合物４の存在は、例えばＸ線光電子分光分析（ＸＰＳ）により確認することができる。また、二次粒子３内部の一次粒子２ｂ、２ｃの表面のホウ素の存在は、例えば、電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）に取り付けた軟Ｘ線発光分光装置（Ｓｏｆｔ　Ｘ－ｒａｙ　Ｅｍｉｓｓｉｏｎ　Ｓｐｅｃｔｒｏｓｃｏｐｙ；ＳＸＥＳ）により、確認することができる。なお、二次粒子内部に存在する微量のホウ素の存在形態は、直接、確認することは困難であるが、ホウ素と化合物を形成する元素としては、リチウムが考えられ、また、二次粒子３の表面に露出する一次粒子２ａの表面においては、ホウ素の少なくとも一部は、リチウムホウ素化合物４の形態で存在することを考慮すると、二次粒子３の内部の一次粒子２ｂ、２ｃの表面においても、リチウムホウ素化合物４（例えば、リチウムホウ素複合酸化物）を形成しているものと推定される。 The presence of the lithium boron compound 4 on the surface of the primary particle 2a exposed on the surface of the secondary particle 3 can be confirmed by, for example, X-ray photoelectron spectroscopy (XPS). Further, the presence of boron on the surface of the primary particles 2b and 2c inside the secondary particle 3 is determined by, for example, a soft X-ray emission spectroscopy apparatus (Soft X-ray emission spectroscopy) attached to a field emission scanning electron microscope (FE-SEM). SXES). Although it is difficult to directly confirm the presence form of a small amount of boron present in the secondary particles, lithium is considered as an element that forms a compound with boron, and the secondary particles 3 Considering that at least part of boron is present in the form of lithium boron compound 4 on the surface of primary particles 2a exposed on the surface, even on the surfaces of primary particles 2b and 2c inside secondary particles 3, It is estimated that the lithium boron compound 4 (for example, lithium boron complex oxide) is formed.
　なお、リチウムホウ素化合物４は、一次粒子２の表面の一部に存在してもよく、一次粒子２の表面全体を被覆してもよい。リチウムホウ素化合物４は、一次粒子２の表面の少なくとも一部に存在すれば、正極抵抗の低減効果が得られる。また、リチウムホウ素化合物４は、一次粒子２の表面に固着していることが好ましい。これにより、リチウムホウ素化合物４とリチウム複合酸化物の一次粒子２との導電性をより高めることができ、正極抵抗の低減効果がより得られる。また、リチウムホウ素化合物４は、図１（Ａ）及び（Ｂ）に示すように、二次粒子３の表面に存在する一次粒子２ａの表面だけでなく、二次粒子３内部の一次粒子２ｂ、２ｃの表面にも形成されることが好ましい。二次粒子３内部の一次粒子２ｂ、２ｃの表面にリチウムホウ素化合物４を形成した場合、リチウムイオンの移動をより促すことができる。 The lithium boron compound 4 may be present on a part of the surface of the primary particle 2 or may cover the entire surface of the primary particle 2. If the lithium boron compound 4 is present on at least a part of the surface of the primary particle 2, the effect of reducing the positive electrode resistance can be obtained. The lithium boron compound 4 is preferably fixed to the surface of the primary particle 2. Thereby, the electroconductivity with the lithium boron compound 4 and the primary particle 2 of lithium composite oxide can be improved more, and the reduction effect of positive electrode resistance is acquired more. In addition, as shown in FIGS. 1A and 1B, the lithium boron compound 4 includes not only the surface of the primary particles 2 a existing on the surface of the secondary particles 3 but also the primary particles 2 b inside the secondary particles 3, It is preferable that it is formed also on the surface of 2c. When the lithium boron compound 4 is formed on the surfaces of the primary particles 2b and 2c in the secondary particle 3, the movement of lithium ions can be further promoted.
　なお、リチウム金属複合酸化物１中のホウ素（Ｂ）の一部は、リチウム金属複合酸化物１の結晶中に固溶してもよい。しかし、すべてのホウ素がリチウム金属複合酸化物１の結晶中に固溶してしまうと、正極抵抗の低減効果が得られない。また、ホウ素がリチウム金属複合酸化物１へ固溶した場合、電池容量の低下が大きくなることがある。 A part of boron (B) in the lithium metal composite oxide 1 may be dissolved in the crystal of the lithium metal composite oxide 1. However, if all the boron is dissolved in the crystal of the lithium metal composite oxide 1, the effect of reducing the positive electrode resistance cannot be obtained. Further, when boron is dissolved in the lithium metal composite oxide 1, the battery capacity may be greatly reduced.
　正極活物質１０は、一次粒子２の表面の水溶性Ｌｉ量が、正極活物質１０全量に対して、０．１質量％以下である。本実施形態の正極活物質１０は、リチウムホウ素化合物４を一次粒子２の表面に形成させ、かつ、水溶性Ｌｉ量が上記範囲であることにより、正極合材ペーストのゲル化を抑制することができる。ここで、正極活物質全量とは、一次粒子２、二次粒子３、リチウムホウ素化合物４、及び、一次粒子２の表面に存在するリチウムホウ素化合物以外のリチウムを含む化合物の合計量を意味する。なお、水溶性Ｌｉ量の下限は、正極活物質全量に対して、例えば０．０１質量％以上である。 In the positive electrode active material 10, the amount of water-soluble Li on the surface of the primary particles 2 is 0.1% by mass or less with respect to the total amount of the positive electrode active material 10. The positive electrode active material 10 of the present embodiment suppresses gelation of the positive electrode mixture paste by forming the lithium boron compound 4 on the surfaces of the primary particles 2 and the amount of water-soluble Li being in the above range. it can. Here, the total amount of the positive electrode active material means the total amount of the primary particles 2, the secondary particles 3, the lithium boron compound 4, and a compound containing lithium other than the lithium boron compound present on the surface of the primary particles 2. In addition, the minimum of the amount of water-soluble Li is 0.01 mass% or more with respect to the positive electrode active material whole quantity, for example.
　正極活物質１０中の水溶性Ｌｉ量は、例えば、後述する正極活物質１０の製造工程において、ホウ素混合工程（ステップＳ４０）で添加するホウ素原料の量や、熱処理工程（ステップＳ５０）の熱処理温度を適宜調整することにより、上記範囲に制御することができる。なお、一次粒子２の表面に存在する水溶性Ｌｉ量は、正極活物質１０に純水を加えて一定時間攪拌した後、純水中に溶出した水溶性Ｌｉ量を、塩酸などにより中和滴定することにより算出できる値である。 The amount of water-soluble Li in the positive electrode active material 10 is, for example, the amount of boron raw material added in the boron mixing step (step S40) or the heat treatment temperature in the heat treatment step (step S50) in the manufacturing process of the positive electrode active material 10 described later. By appropriately adjusting the value, it is possible to control within the above range. The amount of water-soluble Li present on the surfaces of the primary particles 2 is determined by neutralizing titration of the water-soluble Li eluted in pure water after adding pure water to the positive electrode active material 10 and stirring for a certain time with hydrochloric acid or the like. This is a value that can be calculated.
　正極活物質１０は、リチウムホウ素化合物４を含まないリチウム金属複合酸化物と比較して、水溶性Ｌｉ量が増加することがある。図５（Ａ）～（Ｃ）は、後述する実施例及び比較例で得られた正極活物質を用いた二次電池の初期放電容量（図５（Ａ））、正極抵抗（図５（Ｂ））及び、水溶性Ｌｉ量（図５（Ｃ））を示す図である。例えば、図５（Ｃ）に示すように、実施例で得られた正極活物質は、ホウ素（Ｂ）を含まない比較例１の正極活物質と比較して、水溶性Ｌｉ量が増加している。これは、一次粒子２の表面に存在するリチウムホウ素化合物４の量の増加を反映していると考えられ、ホウ素原料が、余剰リチウムと反応するだけでなく、リチウム金属複合酸化物粒子（原料）中の結晶内から引き抜かれたリチウムと反応して、リチウムホウ素化合物４が形成されるためであると考えらえる。 The positive electrode active material 10 may have an increased amount of water-soluble Li as compared with a lithium metal composite oxide not containing the lithium boron compound 4. 5A to 5C show the initial discharge capacity (FIG. 5A) and the positive electrode resistance (FIG. 5B) of secondary batteries using the positive electrode active materials obtained in Examples and Comparative Examples described later. )) And the amount of water-soluble Li (FIG. 5C). For example, as shown in FIG. 5C, the positive electrode active material obtained in the example has an increased amount of water-soluble Li compared to the positive electrode active material of Comparative Example 1 that does not contain boron (B). Yes. This is considered to reflect an increase in the amount of the lithium boron compound 4 present on the surface of the primary particles 2, and the boron raw material not only reacts with excess lithium, but also lithium metal composite oxide particles (raw material). It can be considered that this is because lithium boron compound 4 is formed by reacting with lithium extracted from the inside crystal.
　また、例えば、図５（Ａ）及び（Ｃ）の比較例５に示すように、正極活物質１がホウ素を過剰に含む場合、水溶性Ｌｉ量が多くなり（図５（Ｃ））、かつ、初期放電容量が急激に減少することがある（図５（Ａ））。これは、上述したように、リチウム金属複合酸化物粒子（原料）の結晶内のリチウムが過剰に引き抜かれ、充放電に寄与するリチウムイオンが減少したため、電池容量が低下したと考えられる。 For example, as shown in Comparative Example 5 in FIGS. 5A and 5C, when the positive electrode active material 1 contains excessive boron, the amount of water-soluble Li increases (FIG. 5C), and In some cases, the initial discharge capacity rapidly decreases (FIG. 5A). As described above, it is considered that the battery capacity was lowered because lithium in the crystal of the lithium metal composite oxide particles (raw material) was excessively extracted and lithium ions contributing to charge and discharge were reduced.
　リチウム金属複合酸化物１は、六方晶系の層状結晶構造を有し、その結晶性は、例えば、Ｘ線回折結果のリートベルト解析を行うことによって得られるｃ軸の長さ（以下、「ｃ軸長」ともいう。）や、結晶中のリチウムサイトにおけるリチウム席占有率（以下、「Ｌｉ席占有率」ということがある）などで評価することができる。 The lithium metal composite oxide 1 has a hexagonal layered crystal structure, and the crystallinity thereof is determined by, for example, the length of the c-axis (hereinafter referred to as “c” obtained by performing a Rietveld analysis of the X-ray diffraction result. It can also be evaluated based on the lithium site occupancy at the lithium site in the crystal (hereinafter sometimes referred to as “Li site occupancy”).
　リチウム金属複合酸化物１のＬｉ席占有率は、９６％以上であることが好ましく、９６．５％以上であることがより好ましい。Ｌｉ席占有率を上記範囲に制御した場合、リチウムサイトでのリチウム欠損が抑制されてリチウム複合酸化物粒子の結晶性を高く維持することができる。これにより、得られる二次電池の出力特性を向上させるとともに、高い電池容量を維持することができる。 The Li seat occupancy of the lithium metal composite oxide 1 is preferably 96% or more, and more preferably 96.5% or more. When the Li seat occupancy is controlled within the above range, lithium deficiency at the lithium site can be suppressed and the crystallinity of the lithium composite oxide particles can be maintained high. Thereby, while improving the output characteristic of the obtained secondary battery, high battery capacity can be maintained.
　リチウム金属複合酸化物１は、一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表される。なお、上記一般式（１）は、二次粒子３と、一次粒子２の表面に存在するリチウムホウ素化合物４とを含む、正極活物質１０全体の組成を示す。また、各元素の含有量は、ＩＣＰ発光分光法により測定することができる。 The lithium metal composite oxide 1 has the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (wherein M1 is Li, Ni, Co, Mn, B -0.05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1 0.02 ≦ t ≦ 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5. In addition, the said General formula (1) shows the composition of the positive electrode active material 10 whole containing the secondary particle 3 and the lithium boron compound 4 which exists in the surface of the primary particle 2. FIG. The content of each element can be measured by ICP emission spectroscopy.
　上記一般式（１）中、ホウ素の含有量を示すｔの範囲は、０．０２≦ｔ≦０．０４である。また、ホウ素の少なくとも一部は、上述したように、一次粒子２の表面に、リチウムホウ素化合物として存在する。ｔが上記範囲である場合、正極活物質１０を二次電池の正極に用いた際に、正極抵抗の十分な低減効果が得られるとともに、高い電池容量を得ることができ、ペーストのゲル化を抑制することができる。一方、ｔが０．０２未満の場合、正極抵抗の十分な低減効果が得られず、ペーストのゲル化を抑制することができない。また、ｔが０．０４を超える場合、二次電池の正極抵抗の低減の効果はあるものの、電池容量が急激に低下し、また、ペーストがゲル化することがある。より高い正極抵抗の低減効果と高い電池容量を得るという観点から、前記ｔの範囲を０．０２５≦ｔ≦０．０４とすることが好ましい。 In the general formula (1), the range of t indicating the boron content is 0.02 ≦ t ≦ 0.04. Further, as described above, at least a part of boron is present as a lithium boron compound on the surface of the primary particle 2. When t is in the above range, when the positive electrode active material 10 is used for the positive electrode of the secondary battery, the effect of sufficiently reducing the positive electrode resistance can be obtained and a high battery capacity can be obtained, and the paste can be gelled. Can be suppressed. On the other hand, when t is less than 0.02, the effect of sufficiently reducing the positive electrode resistance cannot be obtained, and gelation of the paste cannot be suppressed. Moreover, when t exceeds 0.04, although there exists an effect of reducing the positive electrode resistance of a secondary battery, a battery capacity | capacitance falls rapidly and a paste may gelatinize. From the viewpoint of obtaining a higher positive electrode resistance reduction effect and a higher battery capacity, the range of t is preferably 0.025 ≦ t ≦ 0.04.
　上記一般式（１）中、ニッケルの含有量を示すｘは、０．１≦ｘ≦０．５であり、好ましくは０．２０≦ｘ≦０．５０である。すなわち、リチウム金属複合酸化物１は、金属元素としてニッケル含み、リチウム以外の金属元素（Ｂを除く）の合計に対して、ニッケルの含有量が１０原子％以上５０原子％以下、好ましくは２０原子％以上５０原子％以下である。リチウム金属複合酸化物１を構成する一次粒子２は、層状岩塩型構造の結晶構造を有する。ニッケルの含有量が上記範囲である場合、正極活物質１０を用いた二次電池は、高い電池容量を実現できる。 In the above general formula (1), x indicating the content of nickel is 0.1 ≦ x ≦ 0.5, preferably 0.20 ≦ x ≦ 0.50. That is, the lithium metal composite oxide 1 contains nickel as a metal element, and the nickel content is 10 to 50 atom%, preferably 20 atoms, with respect to the total of metal elements other than lithium (excluding B). % Or more and 50 atom% or less. The primary particles 2 constituting the lithium metal composite oxide 1 have a layered rock salt type crystal structure. When the nickel content is in the above range, the secondary battery using the positive electrode active material 10 can achieve a high battery capacity.
　上記一般式（１）中、コバルトの含有量を示すｙは、０．１≦ｙ≦０．５であり、好ましくは、０．１５≦ｙ≦０．４５である。すなわち、リチウム金属複合酸化物１は、リチウム以外の金属元素（Ｂを除く）の合計に対して、コバルトの含有量が１０原子％以上５０原子％以下、好ましくは１５原子％以上４５原子％以下である。コバルト含有量が上記範囲である場合、高い結晶構造の安定性を有し、サイクル特性により優れる。 In the general formula (1), y indicating the cobalt content is 0.1 ≦ y ≦ 0.5, and preferably 0.15 ≦ y ≦ 0.45. That is, the lithium metal composite oxide 1 has a cobalt content of 10 atomic% to 50 atomic%, preferably 15 atomic% to 45 atomic%, based on the total of metal elements other than lithium (excluding B). It is. When the cobalt content is in the above range, it has high crystal structure stability and is more excellent in cycle characteristics.
　上記一般式（１）中、マンガンの含有量を示すｚは、０．１≦ｚ≦０．５であり、好ましくは、０．１５≦ｙ≦０．４５である。すなわち、リチウム以外の金属元素（Ｂを除く）の合計に対してマンガンの含有量が１０原子％以上５０原子％以下、好ましくは１５原子％以上４５原子％以下である。マンガンの含有量が上記範囲である場合、高い熱安定性を得ることができる。 In the general formula (1), z indicating the manganese content is 0.1 ≦ z ≦ 0.5, and preferably 0.15 ≦ y ≦ 0.45. That is, the manganese content is 10 atom% or more and 50 atom% or less, preferably 15 atom% or more and 45 atom% or less with respect to the total of metal elements other than lithium (excluding B). When the manganese content is in the above range, high thermal stability can be obtained.
　さらに、電池特性を向上させるため、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素Ｍ１を添加してもよい。例えば、元素Ｍ１は、金属元素であってもよく、元素Ｍ１としてＴｉ、Ｖ、Ｃｒ、Ｚｒ、Ｎｂ、Ｍｏ、Ｈｆ、Ｔａ、Ｆｅ、及びＷから選択される１種以上の金属元素を含有させてもよい。この場合、上記一般式（１）中、元素Ｍの含有量をｕとして、０≦ｕ≦０．１とすることが好ましく、ｘ＋ｙ＋ｚ＋ｕ＝１である。なお、元素Ｍを添加しない場合、上記一般式（１）は、一般式（１）’：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＯ２+β（前記式（１）’中、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＝１、０．０２≦ｔ≦０．０４、及び、０≦β≦０．５を満たす。）で表される。なお、上記式（１）又は一般式（１）’中、βが０であってもよい。 Further, in order to improve battery characteristics, an element M1 other than Li, Ni, Co, Mn, and B may be added. For example, the element M1 may be a metal element, and the element M1 contains one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Fe, and W. May be. In this case, in the general formula (1), the content of the element M is preferably u, and 0 ≦ u ≦ 0.1, and x + y + z + u = 1. In the case where the element M is not added, the general formula (1) is expressed by the general formula (1) ′: Li 1 + s Ni x Co y Mn z B t O 2 + β (in the formula (1) ′, −0. 05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z = 1, 0.02 ≦ t ≦ 0. 04 and 0 ≦ β ≦ 0.5). In the above formula (1) or general formula (1) ′, β may be 0.
　正極活物質１０の平均粒径は、３μｍ以上２０μｍ以下であることが好ましく、４μｍ以上１５μｍ以下であることがより好ましい。平均粒径が上記範囲である場合、得られる二次電池は、高い出力特性および高い電池容量と、正極への高い充填性とをさらに両立させることができる。平均粒径が３μｍ未満である場合、正極への高い充填性が得られないことがあり、平均粒径が２０μｍを超える場合、高い出力特性や電池容量が得られないことがある。 The average particle diameter of the positive electrode active material 10 is preferably 3 μm or more and 20 μm or less, and more preferably 4 μm or more and 15 μm or less. When the average particle size is in the above range, the obtained secondary battery can further achieve both high output characteristics and high battery capacity, and high filling ability to the positive electrode. When the average particle size is less than 3 μm, high filling property to the positive electrode may not be obtained, and when the average particle size exceeds 20 μm, high output characteristics and battery capacity may not be obtained.
　一次粒子２の平均粒径は、０．２μｍ以上１．０μｍ以下であることが好ましく、０．３μｍ以上０．７μｍ以下であることがより好ましい。これにより、電池の正極に用いた際のより高い出力特性と電池容量、さらに高いサイクル特性を得ることができる。一次粒子の平均粒径が０．２μｍ未満になると、高いサイクル特性が得られないことがあり、平均粒径が０．７μｍを超えると、高い出力特性や電池容量が得られないことがある。 The average particle size of the primary particles 2 is preferably 0.2 μm or more and 1.0 μm or less, and more preferably 0.3 μm or more and 0.7 μm or less. Thereby, higher output characteristics and battery capacity when used for the positive electrode of the battery, and higher cycle characteristics can be obtained. When the average particle size of the primary particles is less than 0.2 μm, high cycle characteristics may not be obtained, and when the average particle size exceeds 0.7 μm, high output characteristics and battery capacity may not be obtained.
　ここで、一次粒子２の平均粒径は、二次粒子３の断面を走査型電子顕微鏡（以下、「ＳＥＭ」ともいう。）により観察することで計測できる。二次粒子３の断面観察は、まず、複合水酸化物１を樹脂などに埋め込んだものを切断等して、二次粒子３の断面の試料を作製し、複数の二次粒子３の断面を観察することにより行う。観察する二次粒子３は、複数の二次粒子３の断面において、１つの二次粒子３の断面の外周上で距離が最大となる２点間の距離ｄ（図１参照）が、レーザー光回折散乱式粒度分析計を用いて測定された体積平均粒径（ＭＶ）の８０％以上となる二次粒子３を、任意（無作為）に２０個以上選択したものである。そして、選択したそれぞれの二次粒子３から、さらに任意（無作為）に５０個以上の一次粒子２を選択する。選択した一次粒子２の最長径を計測して粒径を求める。５０個の一次粒子２について、求められたそれぞれの粒径（最長径）を個数平均して、１個の二次粒子３あたりの一次粒子２の粒径（平均）を算出する。さらに、選択した２０個の二次粒子３について、算出されたそれぞれの一次粒子２の粒径（平均）を個数平均することで、正極活物質全体の一次粒子２の平均粒径を算出する。 Here, the average particle diameter of the primary particles 2 can be measured by observing the cross section of the secondary particles 3 with a scanning electron microscope (hereinafter also referred to as “SEM”). For the cross-sectional observation of the secondary particles 3, first, a sample in which the composite hydroxide 1 is embedded in a resin or the like is cut to prepare a sample of the cross-section of the secondary particles 3. This is done by observing. The secondary particle 3 to be observed has a laser beam that has a distance d (see FIG. 1) between two points that has the maximum distance on the outer periphery of the cross section of one secondary particle 3 in the cross section of the plurality of secondary particles 3. 20 or more secondary particles 3 which are 80% or more of the volume average particle diameter (MV) measured using a diffraction scattering particle size analyzer are arbitrarily (randomly) selected. Then, 50 or more primary particles 2 are selected arbitrarily (randomly) from each selected secondary particle 3. The longest diameter of the selected primary particle 2 is measured to determine the particle size. For 50 primary particles 2, the obtained particle diameters (longest diameter) are averaged to calculate the particle diameter (average) of primary particles 2 per secondary particle 3. Furthermore, the average particle diameter of the primary particles 2 of the whole positive electrode active material is calculated by averaging the calculated particle diameters (average) of the respective primary particles 2 for the selected 20 secondary particles 3.
　正極活物質１０の粒度分布の広がりを示す指標である〔（ｄ９０－ｄ１０）／平均粒径〕は、０．６０以下であることが好ましい。これにより、微細粒子や粗大粒子の混入が抑制されて二次粒子の粒径が均一となり、高いサイクル特性が得られる。より高いサイクル特性を得るためには、〔（ｄ９０－ｄ１０）／平均粒径〕が０．５５以下であることが好ましい。〔（ｄ９０－ｄ１０）／平均粒径〕は小さいほど二次粒子の粒径が均一となるが、製造上のばらつきが生じるため、（ｄ９０－ｄ１０）／平均粒径〕の最小値は０．２５程度である。粒度分布の広がりは、例えば、後述する正極活物質の製造工程において、２段階の晶析工程により、晶析を行い、前駆体であるニッケル複合水酸化物を得ることにより、上記範囲とすることができる。 It is preferable that [(d90−d10) / average particle diameter], which is an index indicating the spread of the particle size distribution of the positive electrode active material 10, is 0.60 or less. Thereby, mixing of fine particles and coarse particles is suppressed, the particle size of the secondary particles becomes uniform, and high cycle characteristics are obtained. In order to obtain higher cycle characteristics, it is preferable that [(d90−d10) / average particle diameter] is 0.55 or less. The smaller the [(d90-d10) / average particle size], the more uniform the particle size of the secondary particles. However, because of manufacturing variations, the minimum value of (d90-d10) / average particle size] is 0. About 25. The spread of the particle size distribution should be within the above range by, for example, performing crystallization by a two-stage crystallization process in the manufacturing process of the positive electrode active material described later to obtain a nickel composite hydroxide as a precursor. Can do.
　なお、正極活物質１０の粒径のばらつき指数を示す［（Ｄ９０－Ｄ１０）／平均粒径］において、Ｄ１０は、各粒径における粒子数を粒径の小さい側から累積し、その累積体積が全粒子の合計体積の１０％となる粒径を意味し、Ｄ９０は、同様に粒子数を累積し、その累積体積が全粒子の合計体積の９０％となる粒径を意味する。また、正極活物質の平均粒径は、体積平均粒径（Ｍｖ）を意味する。平均粒径、Ｄ９０及びＤ１０は、レーザー光回折散乱式粒度分析計を用いて測定することができる。 In addition, in [(D90−D10) / average particle diameter] indicating the dispersion index of the particle diameter of the positive electrode active material 10, D10 is the number of particles in each particle diameter accumulated from the smaller particle diameter side, and the accumulated volume is Similarly, D90 means the particle size that accumulates the number of particles and the accumulated volume becomes 90% of the total volume of all particles. Moreover, the average particle diameter of a positive electrode active material means a volume average particle diameter (Mv). The average particle diameters D90 and D10 can be measured using a laser light diffraction / scattering particle size analyzer.
　なお、正極活物質１０は、例えば、図１（Ｂ）に示すように、二次粒子３が、粒内に中空部５を形成した中空構造を有してもよい。中空構造を有する二次粒子３は、例えば、特許文献６などに開示される方法により製造されたリチウム金属複合酸化物粒子を原料として用いることにより、得ることができる。二次粒子３が中空構造を有する場合、二次粒子３の粒内への電解質の侵入がさらに容易となり、高い出力特性がさらに容易に得られる。なお、中空部５は、一つでもよく、複数あってもよい。また、中空構造は、二次粒子３の粒内に多数の空隙を有する多孔質構造も含まれる。 In addition, the positive electrode active material 10 may have a hollow structure in which the secondary particles 3 form hollow portions 5 in the grains, as shown in FIG. 1B, for example. The secondary particles 3 having a hollow structure can be obtained by using, for example, lithium metal composite oxide particles produced by a method disclosed in Patent Document 6 as a raw material. In the case where the secondary particles 3 have a hollow structure, the electrolyte can be more easily penetrated into the particles of the secondary particles 3, and high output characteristics can be obtained more easily. The hollow portion 5 may be one or plural. The hollow structure also includes a porous structure having a large number of voids in the secondary particles 3.
　なお、正極活物質１０は、複数の一次粒子１が凝集して形成される二次粒子２から構成される上記リチウム金属複合酸化物１を含むが、例えば、二次粒子２として凝集しなかった一次粒子１や、凝集後に二次粒子２から脱落した一次粒子１など少量の単独の一次粒子１を含んでもよい。また、正極活物質１０は、本発明の効果を阻害しない範囲で上述したリチウム金属複合酸化物１以外のリチウム金属複合酸化物を含んでもよい。 The positive electrode active material 10 includes the lithium metal composite oxide 1 composed of the secondary particles 2 formed by aggregating a plurality of primary particles 1. For example, the positive electrode active material 10 did not aggregate as the secondary particles 2. A small amount of primary particles 1 such as primary particles 1 or primary particles 1 dropped from secondary particles 2 after aggregation may be included. Moreover, the positive electrode active material 10 may contain lithium metal composite oxide other than the lithium metal composite oxide 1 mentioned above in the range which does not inhibit the effect of this invention.
２．非水系電解質二次電池用正極活物質の製造方法
　本実施形態の正極活物質の製造方法（以下、「製造方法」ともいう。）は、一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物（以下、「リチウム金属複合酸化物」ともいう。）を含む非水系電解質二次電池用正極活物質（以下、「正極活物質」ともいう。）を製造することができる。本実施形態の製造方法により、上記正極活物質１０を、工業的規模で簡便に生産性よく製造することができる。以下、本実施形態の製造方法について、図１及び図２を参照して説明する。 2. Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery The method for producing the positive electrode active material of the present embodiment (hereinafter also referred to as “production method”) is expressed by the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (wherein M1 is an element other than Li, Ni, Co, Mn, and B, −0.05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5.), And includes a lithium nickel cobalt manganese composite oxide (hereinafter also referred to as “lithium metal composite oxide”) having a hexagonal layered crystal structure. A positive electrode active material for a secondary battery (hereinafter also referred to as “positive electrode active material”) can be produced. According to the manufacturing method of the present embodiment, the positive electrode active material 10 can be easily manufactured with high productivity on an industrial scale. Hereinafter, the manufacturing method of this embodiment is demonstrated with reference to FIG.1 and FIG.2.
　本実施形態の製造方法は、図２に示すように、特定の組成を有するニッケルコバルトマンガン複合水酸化物粒子（以下、「複合水酸化物粒子」ともいう。）を晶析により得る晶析工程（ステップＳ１０）と、複合水酸化物粒子に、リチウム化合物を混合してリチウム混合物を得るリチウム混合工程（ステップＳ２０）と、リチウム混合物を、焼成することにより、リチウムニッケルコバルトマンガン複合酸化物粒子（以下、「リチウム金属複合酸化物粒子（原料）」ともいう。）を得る焼成工程（ステップ３０）と、リチウム金属複合酸化物粒子（原料）にホウ素原料を混合してホウ素混合物を得るホウ素混合工程（ステップＳ４０）と、ホウ素混合物を熱処理する熱処理工程（ステップＳ５０）を備えることを特徴とするものである。以下、本発明の製造方法について詳細に説明する。 As shown in FIG. 2, the production method of the present embodiment is a crystallization step of obtaining nickel cobalt manganese composite hydroxide particles (hereinafter also referred to as “composite hydroxide particles”) having a specific composition by crystallization. (Step S10), a lithium mixing step in which a lithium compound is mixed with the composite hydroxide particles to obtain a lithium mixture (Step S20), and the lithium mixture is fired to obtain lithium nickel cobalt manganese composite oxide particles ( Hereinafter, a firing step (step 30) for obtaining “lithium metal composite oxide particles (raw material)” and a boron mixing step for mixing a boron raw material with lithium metal composite oxide particles (raw material) to obtain a boron mixture. (Step S40) and a heat treatment step (Step S50) for heat-treating the boron mixture. Hereinafter, the production method of the present invention will be described in detail.
（晶析工程）
　晶析工程（ステップＳ１０）は、一般式（２）：ＮｉｘＣｏｙＭｎｚＭ２ｕ（ＯＨ）２＋α（前記式（２）中、Ｍ２は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ以外の元素であり、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０≦ｕ≦０．１、及び、０≦α≦０．５を満たす。）で表される複合水酸化物粒子を晶析により得る工程である。晶析の方法は、特に限定されず、公知の晶析方法を用いることができる。通常の晶析方法によって得られる複合水酸化物粒子は、複数の一次粒子が凝集した二次粒子で構成され、この複合水酸化物粒子を用いて得られる正極活物質も複数の一次粒子が凝集した二次粒子で構成されたものとなる。 (Crystallization process)
The crystallization process (step S10) is performed by using the general formula (2): Ni x Co y Mn z M2 u (OH) 2 + α (wherein M2 is an element other than Li, Ni, Co, and Mn. 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0 ≦ u ≦ 0.1, and 0 ≦ α ≦ 0 .5) is obtained by crystallization. The crystallization method is not particularly limited, and a known crystallization method can be used. The composite hydroxide particles obtained by a normal crystallization method are composed of secondary particles in which a plurality of primary particles are aggregated, and the positive active material obtained using the composite hydroxide particles is also aggregated in a plurality of primary particles. The secondary particles are made up of.
　晶析方法としては、例えば、複合水酸化物粒子を晶析法によって工業的に作製する場合、連続晶析法を用いることができる。連続晶析法は、組成の等しい複合水酸化物粒子を大量にかつ簡便に作製できる。しかしながら、連続晶析法は、得られた生成物の粒度分布が比較的幅広い正規分布になりやすく、必ずしも粒径の揃った粒子を得ることができないという課題がある。このような粒度分布が比較的幅広い複合水酸化物粒子を原料としてリチウムイオン二次電池の正極活物質を作製し、リチウムイオン二次電池を組み立てた場合、３μｍ未満の微粉が混入していれば、サイクル特性悪化の要因となりやすい。また、粒度が揃っていないと正極抵抗が増大し、電池出力に悪影響を及ぼす可能性がある。 As the crystallization method, for example, when composite hydroxide particles are produced industrially by a crystallization method, a continuous crystallization method can be used. The continuous crystallization method can easily produce a large amount of composite hydroxide particles having the same composition. However, the continuous crystallization method has a problem that the particle size distribution of the obtained product tends to be a relatively wide normal distribution, and particles having a uniform particle size cannot always be obtained. When a positive electrode active material of a lithium ion secondary battery is produced using composite hydroxide particles having a relatively wide particle size distribution as a raw material and a lithium ion secondary battery is assembled, fine powder of less than 3 μm is mixed. , Easy to cause deterioration of cycle characteristics. Moreover, if the particle size is not uniform, the positive electrode resistance increases, which may adversely affect the battery output.
　晶析の方法としては、粒度分布の制御が容易であるという観点から、例えば、特許文献５に開示されているような、晶析工程（ステップＳ１０）を、核生成工程と粒子成長工程に明確に分離し、二次粒子径の均一化をはかり、粒度分布の狭い複合水酸化物粒子を得ること好ましい。以下、核生成工程と粒子成長工程に分離した晶析方法を説明する。 As a crystallization method, from the viewpoint of easy control of the particle size distribution, for example, the crystallization process (step S10) as disclosed in Patent Document 5 is clearly defined as a nucleation process and a particle growth process. It is preferable to obtain a composite hydroxide particle having a narrow particle size distribution by separating the particles into a uniform particle size. Hereinafter, a crystallization method separated into a nucleation step and a particle growth step will be described.
　　（核生成工程）
　まず、ニッケル、コバルト、マンガン及び、任意に添加元素Ｍ、を含む混合水溶液（以下、「混合水溶液」ともいう。）を作製する。混合水溶液は、例えば、易水溶性のニッケル塩、コバルト塩、マンガン塩及び、任意に添加元素Ｍの塩を所定の割合で水に溶解させて作製する。ニッケル塩、コバルト塩、マンガン塩としては、硫酸塩を用いることが好ましい。なお、添加元素のＭの塩を含む水溶液を混合水溶液に添加すると析出が生じる場合は、添加元素のＭの塩を含む水溶液を準備して、混合水溶液とは別に、後述する反応液に供給してもよい。 (Nucleation process)
First, a mixed aqueous solution (hereinafter, also referred to as “mixed aqueous solution”) containing nickel, cobalt, manganese, and optionally an additional element M is prepared. The mixed aqueous solution is prepared, for example, by dissolving a readily water-soluble nickel salt, cobalt salt, manganese salt, and optionally a salt of the additive element M in water at a predetermined ratio. As the nickel salt, cobalt salt, and manganese salt, sulfate is preferably used. In the case where precipitation occurs when an aqueous solution containing the salt of the additive element M is added to the mixed aqueous solution, an aqueous solution containing the salt of the additive element M is prepared and supplied to the reaction solution described later separately from the mixed aqueous solution. May be.
　次いで、反応槽内へ、混合水溶液と、アンモニウムイオン供給体を含む水溶液と攪拌しながら供給して、反応槽内に反応液を形成し、同時に、アルカリ水溶液を供給して、反応液のｐＨ値が一定となるように制御する。反応液を一定のｐＨ値になるようにアルカリ水溶液量を調節することで、反応中に複合水酸化物粒子の微小な核を選択的に生成させることができる。 Next, the mixed aqueous solution and the aqueous solution containing an ammonium ion supplier are supplied to the reaction tank while stirring to form a reaction liquid in the reaction tank, and at the same time, an alkaline aqueous solution is supplied to adjust the pH value of the reaction liquid Is controlled to be constant. By adjusting the amount of the aqueous alkali solution so that the reaction solution has a constant pH value, minute nuclei of the composite hydroxide particles can be selectively generated during the reaction.
　反応液のｐＨ値は、液温２５℃基準におけるｐＨ値として１２．０以上、好ましくは１２．０以上１４．０以下となるように調節する。ｐＨの値が上記範囲である場合、反応液中に複合水酸化物粒子の微小な核を選択的に生成させることができる。ｐＨ値が１２．０未満である場合、核成長も同時に起こってしまうため、粒度分布も広がりやすく、また、核の総数が不足して粒径が粗大化しやすい。なお、核の総数は、核生成工程におけるｐＨやアンモニア濃度、及び供給される混合水溶液の量によって制御できる。 The pH value of the reaction solution is adjusted so as to be 12.0 or more, preferably 12.0 or more and 14.0 or less as a pH value based on a liquid temperature of 25 ° C. When the pH value is in the above range, fine nuclei of composite hydroxide particles can be selectively generated in the reaction solution. When the pH value is less than 12.0, nucleus growth also occurs at the same time, so that the particle size distribution is likely to be widened, and the total number of nuclei is insufficient and the particle diameter is likely to become coarse. The total number of nuclei can be controlled by the pH and ammonia concentration in the nucleation step and the amount of the mixed aqueous solution supplied.
　反応液中アンモニア濃度は、３ｇ／Ｌ以上１５ｇ／Ｌ以下の範囲内の一定値に保持されることが好ましい。アンモニア濃度が上記範囲に保持される場合、金属イオンの溶解度を一定に保持することができるため、整った水酸化物粒子を形成することができ、ゲル状の核の生成も抑制される。また、粒度分布も所定の範囲に制御できる。一方、アンモニア濃度が１５ｇ／Ｌを超える場合、複合水酸化物粒子が緻密に形成されるため、最終的に得られる正極活物質も緻密な構造になり、比表面積が低くなってしまうことがある。 The ammonia concentration in the reaction solution is preferably maintained at a constant value within a range of 3 g / L to 15 g / L. When the ammonia concentration is maintained within the above range, the solubility of metal ions can be kept constant, so that ordered hydroxide particles can be formed and the formation of gel-like nuclei is also suppressed. Also, the particle size distribution can be controlled within a predetermined range. On the other hand, when the ammonia concentration exceeds 15 g / L, the composite hydroxide particles are densely formed, so that the positive electrode active material finally obtained also has a dense structure and the specific surface area may be low. .
　反応液の温度は、３５℃以上６０℃以下に設定することが好ましい。反応液の温度が３５℃未満の場合、温度が低くて供給する金属イオンの溶解度が十分に得られず、核発生が起こりやすくなり、核発生を制御することが容易でなくなる。また、反応液の温度が６０℃を越える場合、アンモニアの揮発が促進されることにより錯形成するためのアンモニアが不足し、同じように金属イオンの溶解度が減少しやすくなる。なお、核生成工程（ステップＳ１１）におけるｐＨ値と晶析時間については、目的とする複合水酸化物粒子の平均粒径によって任意に設定することができる。 The temperature of the reaction solution is preferably set to 35 ° C. or more and 60 ° C. or less. When the temperature of the reaction solution is less than 35 ° C., the solubility of the metal ions supplied at a low temperature cannot be sufficiently obtained, and nucleation is likely to occur, and it becomes difficult to control the nucleation. On the other hand, when the temperature of the reaction liquid exceeds 60 ° C., the volatilization of ammonia is promoted, so that ammonia for complex formation becomes insufficient, and the solubility of metal ions tends to decrease in the same manner. In addition, about pH value and crystallization time in a nucleation process (step S11), it can set arbitrarily by the average particle diameter of the target composite hydroxide particle.
　（粒子成長工程）
　粒子成長工程では、反応液を液温２５℃基準におけるｐＨ値として１０．５以上１２．０以下、かつ核生成工程より低いｐＨ値に制御する。核形成後にｐＨ値をこの範囲に制御することで、核生成工程で生成した核の成長のみを優先的に起こさせて新たな核形成を抑制することにより、複合水酸化物粒子の粒度の均一性を大幅に向上させることができる。ｐＨ値が１２．０より高い場合には、粒子成長のみでなく、核生成も生じるため、粒度の均一性を大幅に向上させることが難しくなる。一方、ｐＨ値が１０．５未満では、反応液中に残存する金属イオンが増加するため、生産効率が悪化する。また、硫酸塩を原料として用いた場合には、複合水酸化物粒子中に残留する硫黄（Ｓ）分が多くなるため、好ましくない。反応液のアンモニア濃度、温度については、核生成工程と同様の範囲に設定すればよい。 (Particle growth process)
In the particle growth step, the reaction solution is controlled to have a pH value of 10.5 or more and 12.0 or less as a pH value based on a liquid temperature of 25 ° C. and lower than that in the nucleation step. By controlling the pH value within this range after nucleation, only the growth of nuclei generated in the nucleation process is preferentially caused and new nucleation is suppressed, thereby making the particle size of the composite hydroxide particles uniform. Can greatly improve the performance. When the pH value is higher than 12.0, not only particle growth but also nucleation occurs, making it difficult to significantly improve the uniformity of particle size. On the other hand, when the pH value is less than 10.5, the metal ions remaining in the reaction solution increase, so that the production efficiency deteriorates. In addition, when sulfate is used as a raw material, the amount of sulfur (S) remaining in the composite hydroxide particles increases, which is not preferable. What is necessary is just to set the ammonia concentration and temperature of a reaction liquid to the range similar to a nucleation process.
　核生成後あるいは粒子成長段階の途中で、反応液中の液成分の一部を反応槽外に排出することにより、反応液中の複合水酸化物粒子濃度を高めた後、引き続き粒子成長を行うことも可能である。こうすることで、より粒子の粒度分布を狭めることができ、粒子密度も高めることができる。 After nucleation or during the particle growth stage, part of the liquid components in the reaction solution is discharged out of the reaction tank to increase the composite hydroxide particle concentration in the reaction solution, and then continue particle growth. It is also possible. By carrying out like this, the particle size distribution of particle | grains can be narrowed more and particle | grain density can also be raised.
　核生成工程及び粒子成長工程における反応槽内の雰囲気を制御することにより、複合水酸化物粒子を用いて得られる正極活物質の粒子構造を制御することが可能となる。すなわち、雰囲気の酸素濃度を制御することで、複合水酸化物粒子を構成する一次粒子の大きさを制御することが可能であり、複合水酸化物粒子の緻密性を制御することが可能である。したがって、反応槽内の酸素濃度を低減して非酸化性雰囲気とすることにより、複合水酸化物粒子の緻密性が高くなり、得られる正極活物質も緻密性が高くなり中実構造を有するようになる。一方、反応槽内の酸素濃度を高めることで、複合水酸化物粒子の緻密性が低下して、得られる正極活物質は中空構造や多孔質構造を有するようになる。特に、核生成工程と粒子成長工程の初期において反応槽内を酸化性雰囲気とし、その後、非酸化性雰囲気に制御することで、複合水酸化物粒子の中心部の緻密性を低く、外周部の緻密性を高くすることができる。このような複合水酸化物粒子から得られる正極活物質は十分な大きさの中空部を有する中空構造となる。中空部の大きさは、酸化性雰囲気とする時間と非酸化性雰囲気とする時間を調整することにより制御することができる。 By controlling the atmosphere in the reaction vessel in the nucleation step and the particle growth step, the particle structure of the positive electrode active material obtained using the composite hydroxide particles can be controlled. That is, by controlling the oxygen concentration of the atmosphere, it is possible to control the size of the primary particles constituting the composite hydroxide particles, and it is possible to control the compactness of the composite hydroxide particles. . Therefore, by reducing the oxygen concentration in the reaction vessel to make a non-oxidizing atmosphere, the denseness of the composite hydroxide particles becomes higher, and the resulting positive electrode active material also becomes denser and has a solid structure. become. On the other hand, by increasing the oxygen concentration in the reaction vessel, the denseness of the composite hydroxide particles decreases, and the resulting positive electrode active material has a hollow structure or a porous structure. In particular, by making the inside of the reaction vessel an oxidizing atmosphere at the initial stage of the nucleation step and the particle growth step, and then controlling to a non-oxidizing atmosphere, the denseness of the center portion of the composite hydroxide particles is lowered, and the outer peripheral portion The denseness can be increased. The positive electrode active material obtained from such composite hydroxide particles has a hollow structure having a sufficiently large hollow portion. The size of the hollow portion can be controlled by adjusting the time for the oxidizing atmosphere and the time for the non-oxidizing atmosphere.
　上記晶析方法で得られる複合水酸化物粒子は、一般式（２）：ＮｉｘＣｏｙＭｎｚＭ２ｕ（ＯＨ）２＋α（Ｍ２は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ以外の元素であり、ｘ＋ｙ＋ｚ＋ｕ＝１、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、０≦ｕ≦０．１、０≦α≦０．５）で表されるものである。一般式（２）中、Ｍ２は、Ｂを含んでもよいし、含まなくてもよい。また、Ｍ２は、金属元素であってもよく、Ｔｉ、Ｖ、Ｃｒ、Ｚｒ、Ｎｂ、Ｍｏ、Ｈｆ、Ｔａ、Ｆｅ、及びＷから選択される１種以上の金属元素であってもよい。なお、上記式（２）中、αは、複合水酸化物に含まれる金属元素の価数に応じて変化する係数である。複合水酸化物粒子における金属元素の組成比は、正極活物質を構成するリチウム複合酸化物粒子、すなわち、リチウムホウ素化合物をその一次粒子表面に存在させるリチウム金属複合酸化物粒子（原料）の金属元素の組成比まで維持される。したがって、リチウム複合酸化物粒子の組成比となるように複合水酸化物粒子の組成比を調整する。 The composite hydroxide particles obtained by the above crystallization method have the general formula (2): Ni x Co y Mn z M 2 u (OH) 2 + α (M 2 is an element other than Li, Ni, Co, Mn, and x + y + z + u = 1, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, 0 ≦ u ≦ 0.1, 0 ≦ α ≦ 0.5) It is expressed. In general formula (2), M2 may or may not contain B. M2 may be a metal element, or may be one or more metal elements selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, Fe, and W. In the above formula (2), α is a coefficient that changes according to the valence of the metal element contained in the composite hydroxide. The composition ratio of the metal element in the composite hydroxide particle is the lithium composite oxide particle constituting the positive electrode active material, that is, the metal element of the lithium metal composite oxide particle (raw material) in which the lithium boron compound is present on the primary particle surface. The composition ratio is maintained. Therefore, the composition ratio of the composite hydroxide particles is adjusted to be the composition ratio of the lithium composite oxide particles.
　（リチウム混合工程）
　リチウム混合工程（ステップＳ２０）は、上記複合水酸化物粒子と、リチウム化合物とを混合してリチウム混合物を得る工程である。リチウム混合物中のリチウム化合物の含有量は、上記一般式（２）におけるリチウム以外の金属元素の原子数（Ｍｅ）の合計に対するリチウム（Ｌｉ）の原子数の比（Ｌｉ／Ｍｅ）が０．９５以上１．２０以下となるように、混合する。Ｌｉ／Ｍｅが０．９５未満である場合、二次電池における正極抵抗が大きくなり、出力特性が低下してしまう。また、Ｌｉ／Ｍｅが１．２０を超えると、二次電池の初期放電容量が低下するとともに、正極抵抗も増加してしまう。高い放電容量と優れた出力特性を得るという観点から、Ｌｉ／Ｍｅは、１．００以上１．１５以下となるように混合することが好ましい。 (Lithium mixing process)
The lithium mixing step (step S20) is a step of obtaining a lithium mixture by mixing the composite hydroxide particles and the lithium compound. The lithium compound content in the lithium mixture is such that the ratio of the number of atoms of Li (Li) to the total number of atoms (Me) of the metal elements other than lithium in the above general formula (2) (Li / Me) is 0.95. Mix so that it is 1.20 or less. When Li / Me is less than 0.95, the positive electrode resistance in the secondary battery increases and the output characteristics deteriorate. On the other hand, if Li / Me exceeds 1.20, the initial discharge capacity of the secondary battery is reduced and the positive electrode resistance is also increased. From the viewpoint of obtaining a high discharge capacity and excellent output characteristics, it is preferable to mix Li / Me so as to be 1.00 or more and 1.15 or less.
　リチウム化合物は、特に限定されず、公知のものを用いることができ、例えば、水酸化リチウム、炭酸リチウム、又は、その混合物を好適に用いることができる。取り扱いの容易さ、品質の安定性の観点から、リチウム化合物としては、炭酸リチウムを用いることがより好ましい。 The lithium compound is not particularly limited, and a known one can be used. For example, lithium hydroxide, lithium carbonate, or a mixture thereof can be suitably used. From the viewpoint of ease of handling and quality stability, it is more preferable to use lithium carbonate as the lithium compound.
　複合水酸化物粒子とリチウム化合物は、これらを十分混合することが好ましい。混合には、一般的な混合機を使用することができ、例えば、シェーカーミキサーやレーディゲミキサー、ジュリアミキサー、Ｖブレンダーなどを用いることができ、複合酸水化物粒子の形骸が破壊されない程度でリチウム化合物と十分に混合すればよい。 It is preferable that the composite hydroxide particles and the lithium compound are sufficiently mixed. For mixing, a general mixer can be used. For example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used, and the complex acid hydrate particles are not destroyed. What is necessary is just to fully mix with a lithium compound.
　また、リチウム混合物のＬｉ／Ｍｅを正確に制御するため、リチウム化合物と混合する前に複合水酸化物粒子を熱処理して、複合水酸化物粒子の少なくとも一部を複合酸化物粒子に転換してもよい。複合酸化物粒子に転換することで、リチウム化合物と混合する際に含まれる水分量が一定となり、Ｌｉ／Ｍｅが安定する。 In addition, in order to accurately control Li / Me of the lithium mixture, the composite hydroxide particles are heat-treated before mixing with the lithium compound to convert at least a part of the composite hydroxide particles into composite oxide particles. Also good. By converting to composite oxide particles, the amount of water contained when mixing with the lithium compound becomes constant, and Li / Me is stabilized.
　なお、本実施形態の製造方法は、リチウム混合工程（ステップＳ２０）の前に、複合水酸化物粒子を加熱して、複合水酸化物粒子中に残留する水分の一部を除去する工程を含んでもよい。この際の、加熱温度は、例えば、１０５℃以上７００℃以下である。複合水酸化物粒子中に残留する水分の少なくとも一部を除去することにより、焼成工程（ステップＳ３０）で得られる正極活物質のＬｉ／Ｍｅがばらつくことを防ぐことができる。また、上記加熱により、複合水酸化物粒子の少なくとも一部が、複合酸化物粒子に変換されてもよい。また、リチウム混合工程（ステップＳ２０）は、上記複合水酸化物粒及び／又は複合酸化物粒子と、リチウム化合物とを混合してもよい。 In addition, the manufacturing method of this embodiment includes the process of heating a composite hydroxide particle and removing a part of water | moisture content remaining in a composite hydroxide particle before a lithium mixing process (step S20). But you can. The heating temperature at this time is, for example, 105 ° C. or more and 700 ° C. or less. By removing at least part of the moisture remaining in the composite hydroxide particles, it is possible to prevent the Li / Me of the positive electrode active material obtained in the firing step (step S30) from varying. Moreover, at least a part of the composite hydroxide particles may be converted into composite oxide particles by the heating. In the lithium mixing step (step S20), the composite hydroxide particles and / or composite oxide particles may be mixed with a lithium compound.
　（焼成工程）
　次いで、上記リチウム混合物を、酸化性雰囲気中において、８００℃以上１０００℃以下の温度で５時間以上２０時間以下保持して焼成して、複数の一次粒子２が凝集した二次粒子３からなるリチウム金属複合酸化物粒子（原料）を得る（ステップＳ３０）。 (Baking process)
Next, the lithium mixture is calcined in an oxidizing atmosphere at a temperature of 800 ° C. or higher and 1000 ° C. or lower for 5 hours or longer and 20 hours or shorter, and is composed of secondary particles 3 in which a plurality of primary particles 2 are aggregated. Metal composite oxide particles (raw material) are obtained (step S30).
　リチウム混合物の焼成温度は、８００℃以上１０００℃以下である。焼成温度が８００℃未満である場合、複合水酸化物粒子とリチウム化合物との反応が十分に進まず、複合水酸化物粒子中へのリチウムの拡散が十分でなく、余剰のリチウムや未反応の複合酸化物粒子が残ったり、一次粒子中に結晶構造が十分に形成されなかったりして、二次電池の出力特性や電池容量の低下が生じることがある。一方、焼成温度が１０００℃を超えると、二次粒子（原料）間で激しく焼結が生じ、異常粒成長を生じることから粒子が粗大となり、出力特性や電池容量の低下が生じることがある。 The firing temperature of the lithium mixture is 800 ° C. or higher and 1000 ° C. or lower. When the firing temperature is less than 800 ° C., the reaction between the composite hydroxide particles and the lithium compound does not proceed sufficiently, the diffusion of lithium into the composite hydroxide particles is not sufficient, and excess lithium or unreacted The composite oxide particles may remain, or the crystal structure may not be sufficiently formed in the primary particles, resulting in a decrease in output characteristics and battery capacity of the secondary battery. On the other hand, when the firing temperature exceeds 1000 ° C., intense sintering occurs between the secondary particles (raw materials), and abnormal grain growth occurs, so that the particles become coarse, and output characteristics and battery capacity may be reduced.
　上記の焼成温度での保持時間は、５時間以上２０時間以下、好ましくは５時間以上１０時間以下である。保持時間が５時間未満である場合、リチウムニッケルコバルトマンガン複合酸化物からなる二次粒子（原料）の生成が十分に行われな。一方、保持時間が２０時間を超える場合、二次粒子（原料）間で激しく焼結が生じ、異常粒成長を生じ、粒子が粗大となることがある。 The holding time at the above firing temperature is 5 hours or more and 20 hours or less, preferably 5 hours or more and 10 hours or less. When the holding time is less than 5 hours, secondary particles (raw materials) made of lithium nickel cobalt manganese composite oxide are not sufficiently generated. On the other hand, when the retention time exceeds 20 hours, intense sintering occurs between secondary particles (raw materials), abnormal grain growth may occur, and the particles may become coarse.
　焼成時の雰囲気は、酸化性雰囲気であればよいが、酸素濃度が１８容量％以上１００容量％以下であることが好ましい。すなわち、焼成工程（ステップＳ３０）は、大気～酸素気流中で行なうことが好ましく、コストの観点から、空気気流中で行なうことが、より好ましい。酸素濃度が１８容量％未満である場合、酸化が十分でなく、リチウム金属複合酸化物粒子の結晶性が十分でない場合がある。また、焼成に用いられる炉は、特に限定されず、大気～酸素気流中で加熱できるものであればよいが、ガス発生がない電気炉が好ましく、バッチ式又は連続式の炉が用いられる。 The atmosphere during firing may be an oxidizing atmosphere, but the oxygen concentration is preferably 18% by volume or more and 100% by volume or less. That is, the firing step (step S30) is preferably performed in the atmosphere to an oxygen stream, and more preferably in an air stream from the viewpoint of cost. When the oxygen concentration is less than 18% by volume, the oxidation may not be sufficient and the crystallinity of the lithium metal composite oxide particles may not be sufficient. The furnace used for firing is not particularly limited as long as it can be heated in the atmosphere to an oxygen stream, but an electric furnace that does not generate gas is preferable, and a batch type or continuous type furnace is used.
　焼成工程（ステップＳ３０）は、さらに、得られたリチウム金属複合酸化物粒子（原料）を解砕する工程を備えてもよい。上記焼成条件では、得られるリチウム金属複合酸化物粒子（原料）の激しい焼結や異常粒成長は抑制されるが、リチウム金属複合酸化物粒子（原料）間で、軽微な焼結が生じることがある。そこで、焼成後のリチウム金属複合酸化物粒子（原料）を解砕することにより、軽微に凝集（焼結）した二次粒子３同士を分離することができる。解砕は、通常に行われる方法でよく、リチウム金属複合酸化物粒子の二次粒子３を破壊しない程度に行えばよい。 The firing step (step S30) may further include a step of crushing the obtained lithium metal composite oxide particles (raw material). Under the above firing conditions, severe sintering and abnormal grain growth of the obtained lithium metal composite oxide particles (raw material) are suppressed, but slight sintering may occur between the lithium metal composite oxide particles (raw material). is there. Therefore, by crushing the fired lithium metal composite oxide particles (raw material), the slightly aggregated (sintered) secondary particles 3 can be separated. The crushing may be performed by a usual method, and may be performed to such an extent that the secondary particles 3 of the lithium metal composite oxide particles are not destroyed.
　（ホウ素混合工程）
　次いで、上記リチウム複合酸化物粒子（原料）と、ホウ素原料とを混合してホウ素混合物を得る（ステップＳ４０）。ホウ素原料の少なくとも一部は、後の熱処理工程（ステップＳ４０）において、リチウム金属複合酸化物粒子（原料）中のリチウムと反応して、一次粒子２の表面に、リチウムホウ素化合物を形成する。 (Boron mixing process)
Next, the lithium composite oxide particles (raw material) and the boron raw material are mixed to obtain a boron mixture (step S40). At least a part of the boron raw material reacts with lithium in the lithium metal composite oxide particles (raw material) in the subsequent heat treatment step (step S40) to form a lithium boron compound on the surface of the primary particles 2.
　ホウ素混合物中のホウ素含有量は、熱処理工程（ステップＳ４０）後に得られる正極活物質１０中でもほぼ維持される。したがって、ホウ素原料は、目的とする正極活物質１０のホウ素の含有量に見合った量を混合すればよく、例えば、リチウム金属複合酸化物粒子（原料）中のＮｉ、Ｃｏ、Ｍｎの原子数に対して、２ａｔ％以上４ａｔ％以下の範囲で含有される。すなわち、上記一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+βにおいて、ホウ素（Ｂ）の含有量を示すｔの範囲が０．０２≦ｔ≦０．０４となるようにホウ素原料を混合することにより、出力特性の向上と正極合材ペーストのゲル化の抑制とを両立させることができる。また、ホウ素原料をｔが０．０４を超えるように混合する場合、リチウム複合酸化物粒子の結晶中に固溶するホウ素が多くなり過ぎて、電池特性が低下することがある。 The boron content in the boron mixture is substantially maintained even in the positive electrode active material 10 obtained after the heat treatment step (Step S40). Therefore, the boron raw material may be mixed in an amount corresponding to the boron content of the target positive electrode active material 10, for example, the number of atoms of Ni, Co, Mn in the lithium metal composite oxide particles (raw material) On the other hand, it is contained in the range of 2 at% or more and 4 at% or less. That is, in the general formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β , the range of t indicating the content of boron (B) is 0.02 ≦ t ≦ 0.04. By mixing the boron raw material in this manner, it is possible to achieve both improvement in output characteristics and suppression of gelation of the positive electrode mixture paste. Further, when the boron raw material is mixed so that t exceeds 0.04, the amount of boron dissolved in the crystal of the lithium composite oxide particles becomes excessive, and the battery characteristics may be deteriorated.
　用いられるホウ素原料は、ホウ素を含む原料であれば、特に限定されないが、余剰リチウム量の増加を制御して、ペーストのゲル化をより抑制するという観点から、リチウムを含まないホウ素原料を用いることが好ましい。ホウ素原料としては、例えば、ホウ素及び酸素を含む化合物を用いることができ、取扱いが容易であり、品質の安定性に優れるという観点から、好ましくは、酸化ホウ素、ホウ素のオキソ酸及びこれらの混合物を用いることが好ましく、オルトホウ酸を用いることがより好ましい。 The boron raw material to be used is not particularly limited as long as it is a raw material containing boron, but from the viewpoint of controlling the increase in the amount of excess lithium and further suppressing gelation of the paste, use a boron raw material that does not contain lithium. Is preferred. As the boron raw material, for example, a compound containing boron and oxygen can be used, and from the viewpoint of easy handling and excellent quality stability, it is preferable to use boron oxide, boron oxo acid and a mixture thereof. It is preferable to use orthoboric acid, and it is more preferable to use orthoboric acid.
　リチウム複合酸化物粒子（原料）と、ホウ素原料との混合には、一般的な混合機を使用することができ、例えばシェーカーミキサーやレーディゲミキサー、ジュリアミキサー、Ｖブレンダーなどを用いることができる。混合は、リチウム複合酸化物粒子の形骸が破壊されない程度でリチウム複合酸化物粒子（原料）とホウ素原料と十分に混合してやればよい。また、焼成工程（ステップＳ４０）において、リチウム複合酸化物粒子（原料）間で均一にホウ素を含有させるため、ホウ素混合物中にリチウム複合酸化物粒子とホウ素原料とが均一に分散されるように、十分混合することが好ましい。 For mixing the lithium composite oxide particles (raw material) and the boron raw material, a general mixer can be used. For example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used. . The mixing may be performed by sufficiently mixing the lithium composite oxide particles (raw material) and the boron raw material to such an extent that the shape of the lithium composite oxide particles is not destroyed. Further, in the firing step (step S40), in order to uniformly contain boron among the lithium composite oxide particles (raw material), so that the lithium composite oxide particles and the boron raw material are uniformly dispersed in the boron mixture, It is preferable to mix thoroughly.
　（熱処理工程）
　次いで、上記ホウ素混合物を、大気雰囲気中において２００℃以上３００℃以下の温度で、熱処理し、リチウム金属複合酸化物１を得る（ステップＳ５０）。上記温度範囲で熱処理する場合、ホウ素原料と、リチウム金属複合酸化物粒子（原料）の一次粒子の表面に存在する未反応のリチウム化合物や一次粒子の結晶内の過剰なリチウムと、を反応させて、二次粒子３内にホウ素を拡散させ、一次粒子の表面にリチウムホウ素化合物４が形成される。得られたリチウム金属複合酸化物１を用いた正極活物質１０は、二次電池の正極抵抗が低減されるとともに、正極合材ペーストのゲル化を抑制することができる。 (Heat treatment process)
Next, the boron mixture is heat-treated at a temperature of 200 ° C. or higher and 300 ° C. or lower in an air atmosphere to obtain the lithium metal composite oxide 1 (step S50). When the heat treatment is performed in the above temperature range, the boron raw material is reacted with the unreacted lithium compound present on the surface of the primary particles of the lithium metal composite oxide particles (raw material) or excessive lithium in the crystals of the primary particles. Then, boron is diffused into the secondary particles 3, and the lithium boron compound 4 is formed on the surface of the primary particles. The positive electrode active material 10 using the obtained lithium metal composite oxide 1 can reduce the positive electrode resistance of the secondary battery and suppress gelation of the positive electrode mixture paste.
　一方、２００℃未満の温度で熱処理した場合、ホウ素原料と、リチウム金属複合酸化物粒子中のリチウムとの反応が十分でなく、未反応のホウ素原料が残存する、あるいはリチウムホウ素化合物が十分に形成されず、上述のような正極抵抗の低減効果が得られない。また、３００℃を超える温度で熱処理温度した場合、得られた正極活物質を用いた正極合材ペーストのゲル化が十分抑制されず、二次電池の電池容量も低下する。この理由は、特に限定されないが、例えば、ホウ素が一次粒子表面の未反応リチウム（余剰リチウム）と反応するだけでなく、一次粒子の結晶内のリチウムとも過剰に反応して、一次粒子内のリチウムが引き抜かれ過ぎる状態となり、充放電に寄与するリチウムイオンが減少し、かつ、一次粒子の表面に正極合材ペーストのゲル化に寄与する水溶性Ｌｉの量が増加するためと考えらえる。 On the other hand, when heat treatment is performed at a temperature lower than 200 ° C., the reaction between the boron raw material and lithium in the lithium metal composite oxide particles is not sufficient, and the unreacted boron raw material remains or the lithium boron compound is sufficiently formed. In other words, the positive electrode resistance reduction effect as described above cannot be obtained. Moreover, when it heat-processes at the temperature exceeding 300 degreeC, gelatinization of the positive mix paste using the obtained positive electrode active material is not fully suppressed, and the battery capacity of a secondary battery also falls. The reason for this is not particularly limited. For example, boron not only reacts with unreacted lithium (surplus lithium) on the surface of the primary particles, but also reacts excessively with lithium in the crystals of the primary particles, so that lithium in the primary particles This is considered to be because the lithium ions contributing to charge / discharge are reduced, and the amount of water-soluble Li contributing to the gelation of the positive electrode mixture paste on the surface of the primary particles is increased.
　熱処理工程（ステップＳ５０）では、上記温度範囲で熱処理するとともに、一次粒子２の表面（全体）に存在する水溶性Ｌｉ量が、熱処理前に対して、熱処理後に１．３倍以下となるように、熱処理条件を調整して熱処理を行う。水溶性Ｌｉ量が上記範囲である場合、一次粒子の結晶内のリチウムが過剰に引き抜かれることが抑制され、リチウム複合酸化物粒子の結晶性を維持することができる。また、リチウムホウ素化合物の過剰な生成を抑制し、正極合材ペーストのゲル化を抑制することができる。一方、水溶性Ｌｉ量が上記範囲を超える場合、リチウム複合酸化物粒子の結晶内のリチウムが過剰に引き抜かれてリチウムホウ素化合物が形成されることで、検出される余剰リチウム量が増加する。水溶性Ｌｉ量は、例えば、ホウ素原料の添加量に合わせて、熱処理時間を調整することで制御することができる。なお、熱処理後の水溶性Ｌｉ量の下限値は、熱処理前に対して、１倍以上であり、１．３倍以下であることが好ましい。なお、熱処理後の水溶性Ｌｉ量の増加量は、上述したように、一次粒子２の表面のリチウムホウ素化合物４の形成された量を反映していると考えられる。 In the heat treatment step (step S50), the heat treatment is performed in the above temperature range, and the amount of water-soluble Li present on the surface (whole) of the primary particles 2 is 1.3 times or less after the heat treatment with respect to that before the heat treatment. The heat treatment is performed by adjusting the heat treatment conditions. When the amount of the water-soluble Li is in the above range, excessive extraction of lithium in the primary particle crystals is suppressed, and the crystallinity of the lithium composite oxide particles can be maintained. Moreover, the excessive production | generation of a lithium boron compound can be suppressed and the gelatinization of a positive mix paste can be suppressed. On the other hand, when the amount of water-soluble Li exceeds the above range, lithium in the lithium composite oxide particles is excessively extracted to form a lithium boron compound, thereby increasing the amount of detected excess lithium. The amount of water-soluble Li can be controlled, for example, by adjusting the heat treatment time in accordance with the amount of boron raw material added. In addition, the lower limit of the amount of water-soluble Li after the heat treatment is 1 time or more and preferably 1.3 times or less that before the heat treatment. In addition, it is thought that the increase amount of the water-soluble Li amount after heat treatment reflects the amount of the lithium boron compound 4 formed on the surface of the primary particle 2 as described above.
　熱処理時間は、余剰リチウムの形成量に合わせて適宜調整できるが、好ましくは５時間以上２０時間以下であり、より好ましくは５時間以上１０時間以下である。熱処理時間が上記範囲である場合、リチウムホウ素化合物４を十分に生成させ、二次電池の出力特性をさらに向上することができる。一方、熱処理時間が５時間未満の場合、リチウムホウ素化合物が十分に生成されないことがある。また、熱処理時間が２０時間を超える場合、リチウム複合酸化物粒子の結晶内のリチウムが引き抜かれ過ぎることがある。 The heat treatment time can be appropriately adjusted according to the amount of surplus lithium formed, but is preferably 5 hours or more and 20 hours or less, more preferably 5 hours or more and 10 hours or less. When heat processing time is the said range, the lithium boron compound 4 can fully be produced | generated and the output characteristic of a secondary battery can further be improved. On the other hand, when the heat treatment time is less than 5 hours, the lithium boron compound may not be sufficiently generated. When the heat treatment time exceeds 20 hours, lithium in the crystal of the lithium composite oxide particles may be excessively extracted.
　熱処理時の雰囲気は、酸化性雰囲気であればよいが、酸素濃度が１８容量％以上１００容量％以下であることが好ましい。すなわち、熱処理工程（ステップＳ５０）は、大気～酸素気流中で行なうことが好ましく、コストの観点から、空気気流中で行なうことが、より好ましい。酸素濃度が１８容量％未満である場合、リチウムホウ素化合物の形成が十分でないことがある。また、熱処理に用いられる炉は、上記焼成工程で用いられる炉と同様の炉を用いることができる。 The atmosphere during the heat treatment may be an oxidizing atmosphere, but the oxygen concentration is preferably 18% by volume or more and 100% by volume or less. That is, the heat treatment step (step S50) is preferably performed in the atmosphere to an oxygen stream, and more preferably in an air stream from the viewpoint of cost. When the oxygen concentration is less than 18% by volume, the formation of the lithium boron compound may not be sufficient. Moreover, the furnace similar to the furnace used by the said baking process can be used for the furnace used for heat processing.
３．非水系電解質二次電池
　本実施形態の非水系電解質二次電池（以下、「二次電池」ともいう。）は、上述の正極活物質を正極に用いることにより、出力特性及び電池量の向上と、二次電池を作製する際の正極合材ペーストのゲル化の抑制と、を両立することができる。以下、本実施形態の二次電池の一例について、構成要素ごとにそれぞれ説明する。本実施形態の二次電池は、公知のリチウムイオン二次電池と同様の構成要素から構成されることができ、例えば、正極、負極及び非水電解液を含む。なお、以下で説明する実施形態は例示に過ぎず、非水系電解質二次電池は、下記実施形態をはじめとして、当業者の知識に基づいて種々の変更、改良を施した形態で実施することができる。また、本実施形態の二次電池は、その用途を特に限定するものではない。 3. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery (hereinafter, also referred to as “secondary battery”) of the present embodiment uses the positive electrode active material described above as a positive electrode, thereby improving output characteristics and battery amount. In addition, it is possible to achieve both suppression of gelation of the positive electrode mixture paste when producing a secondary battery. Hereinafter, an example of the secondary battery of the present embodiment will be described for each component. The secondary battery of this embodiment can be comprised from the component similar to a well-known lithium ion secondary battery, for example, contains a positive electrode, a negative electrode, and a non-aqueous electrolyte. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery may be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiment. it can. Moreover, the use of the secondary battery of this embodiment is not particularly limited.
（正極）
　上記の正極活物質を用いて、二次電池の正極を作製する。以下に正極の製造方法の一例を説明する。まず、上記の正極活物質（粉末状）、導電材および結着剤（バインダー）を混合し、さらに必要に応じて、活性炭や、溶剤を添加し、これを混練して正極合材ペーストを作製する。 (Positive electrode)
A positive electrode of a secondary battery is manufactured using the positive electrode active material. Below, an example of the manufacturing method of a positive electrode is demonstrated. First, the positive electrode active material (powder), conductive material and binder (binder) are mixed, and if necessary, activated carbon or a solvent is added and kneaded to prepare a positive electrode mixture paste. To do.
　正極合材中のそれぞれの材料の混合比は、リチウム二次電池の性能を決定する要素となるため、用途に応じて、調整することができる。材料の混合比は、公知のリチウム二次電池の正極と同様とすることができ、例えば、溶剤を除いた正極合材の固形分の全質量を１００質量％とした場合、正極活物質を６０～９５質量％、導電材を１～２０質量％、結着剤を１～２０質量％含有することができる。 Since the mixing ratio of each material in the positive electrode mixture is an element that determines the performance of the lithium secondary battery, it can be adjusted according to the application. The mixing ratio of the materials can be the same as that of the positive electrode of a known lithium secondary battery. For example, when the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the positive electrode active material is 60%. Up to 95% by mass, 1 to 20% by mass of a conductive material, and 1 to 20% by mass of a binder can be contained.
　導電材としては、例えば、黒鉛（天然黒鉛、人造黒鉛および膨張黒鉛など）や、アセチレンブラックやケッチェンブラックなどのカーボンブラック系材料などを用いることができる。 As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), carbon black materials such as acetylene black and ketjen black, and the like can be used.
　結着剤（バインダー）としては、活物質粒子をつなぎ止める役割を果たすもので、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、フッ素ゴム、エチレンプロピレンジエンゴム、スチレンブタジエン、セルロース系樹脂およびポリアクリル酸などを用いることができる。 As the binder (binder), it plays the role of holding the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluoro rubber, ethylene propylene diene rubber, styrene butadiene, cellulose series Resins and polyacrylic acid can be used.
　正極合材ペーストは、必要に応じ、活性炭や溶剤を添加することができる。例えば、正極活物質、導電材および活性炭を分散させて、結着剤を溶解する溶剤を正極合材に添加して、正極合材ペーストを得ることができる。正極合材に活性炭を添加することにより、電気二重層容量を増加させることができる。また、溶剤は、決着剤を溶解し、正極合材ペーストの粘度等を調整することができる。溶剤は、例えば、Ｎ－メチル－２－ピロリドン（ＮＭＰ）などの有機溶剤を用いることができる。 The activated carbon paste can be added to the positive electrode mixture paste as necessary. For example, a positive electrode mixture paste can be obtained by dispersing a positive electrode active material, a conductive material, and activated carbon, and adding a solvent that dissolves the binder to the positive electrode mixture. The electric double layer capacity can be increased by adding activated carbon to the positive electrode mixture. Further, the solvent can dissolve the fixing agent and adjust the viscosity and the like of the positive electrode mixture paste. As the solvent, for example, an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used.
　次いで、得られた正極合材ペーストを、例えば、アルミニウム箔製の集電体の表面に塗布し、乾燥して溶剤を飛散させ、シート状の正極が作成される。必要に応じ、電極密度を高めるべくロールプレス等により加圧することもある。このようにして得られたシート状の正極は、目的とする電池に応じて適当な大きさに裁断等し、電池の作製に供することができる。なお、正極の作製方法は、上記のものに限られることなく、他の製造方法を用いてもよい。 Next, the obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, an aluminum foil, and dried to disperse the solvent, thereby producing a sheet-like positive electrode. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. The sheet-like positive electrode thus obtained can be cut into an appropriate size according to the target battery and used for battery production. In addition, the manufacturing method of a positive electrode is not restricted to the above-mentioned thing, You may use another manufacturing method.
（負極）
　負極は、金属リチウム、リチウム合金等を用いることができる。また、負極は、リチウムイオンを吸蔵・脱離できる負極活物質に結着剤を混合し、適当な溶剤を加えてペースト状にした負極合材を、銅等の金属箔集電体の表面に塗布、乾燥し、必要に応じて電極密度を高めるべく圧縮して形成したものを用いてもよい。 (Negative electrode)
For the negative electrode, metallic lithium, a lithium alloy, or the like can be used. The negative electrode is prepared by mixing a negative electrode active material capable of occluding and desorbing lithium ions with a binder and adding a suitable solvent to form a paste on the surface of a metal foil current collector such as copper. You may use what was formed by compressing in order to apply | coat, dry and to raise an electrode density as needed.
　負極活物質としては、例えば、天然黒鉛、人造黒鉛およびフェノール樹脂などの有機化合物焼成体、およびコークスなどの炭素物質の粉状体を用いることができる。この場合、負極結着剤としては、正極同様、ＰＶＤＦなどの含フッ素樹脂を用いることができ、これらの活物質および結着剤を分散させる溶剤としては、Ｎ－メチル－２－ピロリドンなどの有機溶剤を用いることができる。 As the negative electrode active material, for example, a fired organic compound such as natural graphite, artificial graphite, and phenol resin, and a powdery carbon material such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder as in the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.
（セパレータ）
　正極と負極との間には、セパレータを挟み込んで配置する。セパレータは、正極と負極とを分離し、電解質を保持するものであり、公知のものを用いることができ、例えば、ポリエチレンやポリプロピレンなどの薄い膜で、微少な孔を多数有する膜を用いることができる。 (Separator)
A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and holds the electrolyte, and a known one can be used. For example, a thin film such as polyethylene or polypropylene and a film having a large number of minute holes can be used. it can.
（非水系電解液）
　非水系電解液は、支持塩としてのリチウム塩を有機溶媒に溶解したものである。有機溶媒としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネートおよびトリフルオロプロピレンカーボネートなどの環状カーボネート、また、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネートおよびジプロピルカーボネートなどの鎖状カーボネート、さらに、テトラヒドロフラン、２－メチルテトラヒドロフランおよびジメトキシエタンなどのエーテル化合物、エチルメチルスルホンやブタンスルトンなどの硫黄化合物、リン酸トリエチルやリン酸トリオクチルなどのリン化合物などから選ばれる１種を単独、又は２種以上を混合して用いることができる。 (Non-aqueous electrolyte)
The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, tetrahydrofuran, 2- Use one kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can do.
　支持塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＮ（ＣＦ３ＳＯ２）２、およびそれらの複合塩などを用いることができる。さらに、非水系電解液は、ラジカル捕捉剤、界面活性剤および難燃剤などを含んでいてもよい。 As the supporting salt, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , and complex salts thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.
（電池の形状、構成）
　以上のように説明してきた正極、負極、セパレータおよび非水系電解液で構成される本発明の非水系電解質二次電池は、円筒形や積層形など、種々の形状にすることができる。
　いずれの形状を採る場合であっても、正極および負極を、セパレータを介して積層させて電極体とし、得られた電極体に、非水系電解液を含浸させ、正極集電体と外部に通ずる正極端子との間、および、負極集電体と外部に通ずる負極端子との間を、集電用リードなどを用いて接続し、電池ケースに密閉して、非水系電解質二次電池を完成させる。 (Battery shape and configuration)
The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte described above can have various shapes such as a cylindrical shape and a laminated shape.
In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the nonaqueous electrolyte secondary battery. .
（二次電池の形状、構成）
　本実施形態の二次電池の形状は、特に限定されず円筒形や積層形など、種々の形状にすることができる。いずれの形状を採る場合であっても、二次電池は、上述した正極、負極、セパレータおよび非水系電解液で構成されることができる。二次電池の製造方法は、特に限定されず、例えば、正極および負極を、セパレータを介して積層させて電極体とし、得られた電極体に、非水系電解液を含浸させ、正極集電体と外部に通ずる正極端子との間、および、負極集電体と外部に通ずる負極端子との間を、集電用リードなどを用いて接続し、電池ケースに密閉して、製造される。 (Secondary battery shape and configuration)
The shape of the secondary battery of the present embodiment is not particularly limited, and can be various shapes such as a cylindrical shape and a stacked shape. Even if it takes any shape, a secondary battery can be comprised with the positive electrode mentioned above, a negative electrode, a separator, and nonaqueous electrolyte solution. The manufacturing method of the secondary battery is not particularly limited, and for example, a positive electrode and a negative electrode are laminated through a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte solution, and a positive electrode current collector is obtained. And a positive electrode terminal that communicates with the outside and a negative electrode current collector and a negative electrode terminal that communicates with the outside using a current collecting lead or the like, and sealed in a battery case.
（二次電池の特性）
　本実施形態の二次電池は、上記正極活物質１０を用いた正極を有するため、高容量であり、かつ、出力特性に優れる。また、二次電池に用いられる正極活物質１０は、工業的な製造方法で得ることができるため、生産性に非常に優れる。本実施形態の二次電池の用途は特に限定されないが、例えば、常に高容量を要求される小型携帯電子機器（ノート型パーソナルコンピュータや携帯電話端末など）の電源に好適に用いることができる。 (Characteristics of secondary battery)
Since the secondary battery of this embodiment has a positive electrode using the positive electrode active material 10, it has a high capacity and excellent output characteristics. Moreover, since the positive electrode active material 10 used for a secondary battery can be obtained with an industrial manufacturing method, it is very excellent in productivity. Although the use of the secondary battery of this embodiment is not particularly limited, for example, it can be suitably used as a power source for small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require high capacity.
　また、本実施形態の二次電池は、従来のリチウムコバルト系酸化物あるいはリチウムニッケル系酸化物の正極活物質を正極に用いた二次電池と比較した場合、熱安定性がより高く、安全性に優れており、かつ、高容量で出力特性に優れている。そのため、上記の正極活物質１０を用いた二次電池は、小型化、高出力化が可能であり、例えば、搭載スペースに制約を受ける電気自動車用電源として好適に用いることができる。 In addition, the secondary battery of the present embodiment has higher thermal stability and safety when compared with a secondary battery using a positive electrode active material of a conventional lithium cobalt oxide or lithium nickel oxide as a positive electrode. In addition, it has a high capacity and excellent output characteristics. Therefore, the secondary battery using the positive electrode active material 10 can be reduced in size and output, and can be suitably used as, for example, a power source for an electric vehicle that is restricted by a mounting space.
　さらに、本実施形態の二次電池は、純粋に電気エネルギーで駆動する電気自動車用の電源のみならず、例えば、ガソリンエンジンやディーゼルエンジンなどの燃焼機関と併用するいわゆるハイブリッド車用の電源としても用いることができる。 Furthermore, the secondary battery of the present embodiment is used not only as a power source for an electric vehicle driven purely by electric energy but also as a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. be able to.
　以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、実施例及び比較例における正極活物質に含有される金属の分析方法及び評価方法は、以下の通りである。 Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis method and evaluation method of the metal contained in the positive electrode active material in an Example and a comparative example are as follows.
（１）組成の分析：ＩＣＰ発光分析法で測定した。
（２）平均粒径、および〔（ｄ９０－ｄ１０）／平均粒径〕：
　正極活物質の平均粒径、および〔（ｄ９０－ｄ１０）／平均粒径〕の測定は、レーザー回折散乱式粒度分布測定装置（日機装株式会社製、マイクロトラックＨＲＡ）により行なった。正極活物質の平均粒径は、体積平均粒径ＭＶを用いた。また、一次粒子の平均粒径は、レーザー光回折散乱式粒度分析計を用いて測定された体積平均粒径ＭＶの８０％以上となる二次粒子（任意に２０個選択）の断面を走査型電子顕微鏡（ＳＥＭ）により観察し、各二次粒子あたり、任意に５０個の一次粒子の粒径（最長径）を測定した。測定された粒径を個数平均して、各二次粒子あたりの一次粒子の粒径（平均）を算出した。さらに、２０個の二次粒子について、算出された各二次粒子あたりの一次粒子の粒径（平均）を個数平均して、正極活物質全体の一次粒子の平均粒径を求めた。
（３）初期放電容量：
　初期放電容量は、コイン型電池を作製してから２４時間程度放置し、開回路電圧ＯＣＶ（ｏｐｅｎ　ｃｉｒｃｕｉｔ　ｖｏｌｔａｇｅ）が安定した後、正極に対する電流密度を０．１ｍＡ／ｃｍ２としてカットオフ電圧４．３Ｖまで充電し、１時間の休止後、カットオフ電圧３．０Ｖまで放電したときの容量とした。放電容量の測定には，マルチチャンネル電圧／電流発生器（株式会社アドバンテスト製、Ｒ６７４１Ａ）を用いた。
（４）反応抵抗：
　反応抵抗は、測定温度に温度調節したコイン型電池を充電電位４．１Ｖで充電して、交流インピーダンス法により抵抗値を測定した。測定には、周波数応答アナライザおよびポテンショガルバノスタット（ソーラトロン製、１２５５Ｂ）を使用して、図７に示すナイキストプロットを作成し、図８に示した等価回路を用いてフィッティング計算して、正極抵抗（反応抵抗）の値を算出した。
（５）水溶性のＬｉ量の測定：
　得られた正極活物質の一次粒子表面に存在する水溶性のＬｉ量について、正極活物質から溶出してくるＬｉの量を中和滴定することにより評価した。得られた正極活物質に純水を加えて一定時間攪拌後、ろ過したろ液のｐＨを測定しながら塩酸を加えていくことにより測定し、加えた塩酸の量から水溶性Ｌｉ量を算出した。
（６）正極合材ペーストの粘度安定性
　正極活物質２５．０ｇと、導電材のカーボン粉１．５ｇと、ポリフッ化ビニリデン（ＰＶＤＦ）２．９ｇと、Ｎ－メチル－２ピロリドン（ＮＭＰ）とを遊星運動混練機により混合し正極合材ペーストを得た。Ｎ－メチル－２ピロリドン（ＮＭＰ）は、ＪＩＳ　Ｚ　８８０３：２０１１に規定される振動粘度計による粘度測定方法により、粘度が１．５～２．５Ｐａ・ｓとなるように添加量を調整した。得られたペーストを７６時間保管してゲル化の発生状況を目視で評価し、ゲル化が発生していないものを○、ゲル化が発生したものを×とした。
（７）リチウムホウ素化合物の検出
　正極活物質の表面をＸＰＳ（アルバック・ファイ社製、ＶｅｒｓａＰｒｏｂｅ　ＩＩ）で分析した。ホウ素のピークにリチウムとの化合を示す波形が確認された場合、正極活物質（一次粒子）の表面にリチウムホウ素化合物が形成されていると判断した。 (1) Composition analysis: Measured by ICP emission spectrometry.
(2) Average particle size and [(d90-d10) / average particle size]:
The average particle size of the positive electrode active material and [(d90-d10) / average particle size] were measured with a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac HRA). As the average particle diameter of the positive electrode active material, the volume average particle diameter MV was used. The average particle size of the primary particles is a scanning type of a cross-section of secondary particles (arbitrarily 20 particles selected) that are 80% or more of the volume average particle size MV measured using a laser light diffraction / scattering particle size analyzer. Observation was made with an electron microscope (SEM), and the particle size (longest diameter) of 50 primary particles was arbitrarily measured for each secondary particle. The number average of the measured particle diameter was averaged to calculate the particle diameter (average) of primary particles for each secondary particle. Further, for the 20 secondary particles, the average particle diameter (average) of the calculated primary particles for each secondary particle was averaged to obtain the average primary particle diameter of the entire positive electrode active material.
(3) Initial discharge capacity:
The initial discharge capacity is left for about 24 hours after the coin-type battery is produced, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is set to 0.1 mA / cm 2 and the cut-off voltage is 4. It was set as the capacity | capacitance when it charged to 3V, and discharged to the cut-off voltage 3.0V after 1 hour rest. For the measurement of the discharge capacity, a multi-channel voltage / current generator (manufactured by Advantest Corporation, R6741A) was used.
(4) Reaction resistance:
For the reaction resistance, a coin-type battery whose temperature was adjusted to the measurement temperature was charged at a charging potential of 4.1 V, and the resistance value was measured by an AC impedance method. For the measurement, a Nyquist plot shown in FIG. 7 is created using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B), and fitting calculation is performed using the equivalent circuit shown in FIG. The value of (reaction resistance) was calculated.
(5) Measurement of water-soluble Li content:
The amount of water-soluble Li present on the surface of the primary particles of the obtained positive electrode active material was evaluated by neutralizing and titrating the amount of Li eluted from the positive electrode active material. After adding pure water to the obtained positive electrode active material and stirring for a certain time, it was measured by adding hydrochloric acid while measuring the pH of the filtered filtrate, and the amount of water-soluble Li was calculated from the amount of added hydrochloric acid. .
(6) Viscosity stability of positive electrode composite paste 25.0 g of positive electrode active material, 1.5 g of carbon powder of conductive material, 2.9 g of polyvinylidene fluoride (PVDF), N-methyl-2-pyrrolidone (NMP) Were mixed with a planetary motion kneader to obtain a positive electrode mixture paste. The amount of N-methyl-2pyrrolidone (NMP) added was adjusted so that the viscosity would be 1.5 to 2.5 Pa · s by a viscosity measurement method using a vibration viscometer specified in JIS Z 8803: 2011. The obtained paste was stored for 76 hours, and the occurrence of gelation was visually evaluated. The case where gelation did not occur was evaluated as ◯, and the case where gelation occurred was evaluated as x.
(7) Detection of Lithium Boron Compound The surface of the positive electrode active material was analyzed by XPS (manufactured by ULVAC-PHI, VersaProbe II). When the waveform which shows a compound with lithium was confirmed in the peak of boron, it was judged that the lithium boron compound was formed in the surface of a positive electrode active material (primary particle).
　（実施例１）
（晶析工程）
　まず、反応槽（６０Ｌ）内に水を半分の量まで入れて大気雰囲気中で撹拌しながら、槽内温度を４０℃に設定し、そこへ２５質量％水酸化ナトリウム水溶液と２５質量％アンモニア水を適量加えて、槽内の液のｐＨ値を、液温２５℃基準で１２．８に、液中のアンモニア濃度を１０ｇ／Ｌに調節した。ここに、硫酸ニッケル、硫酸コバルト、硫酸マンガンの２．０ｍｏｌ／Ｌの混合水溶液（金属元素モル比でＮｉ：Ｃｏ：Ｍｎ＝３８：３２：３０）を１３０ｍｌ／分の割合で加えて反応水溶液とした。同時に、２５質量％アンモニア水および２５質量％水酸化ナトリウム水溶液を一定速度で加えていき、ｐＨ値を１２．８（核生成ｐＨ）に制御しながら２分３０秒間晶析を行った。その後、窒素ガスを流通させ反応槽内の酸素濃度を２容量％以下まで低下させながら、ｐＨ値が液温２５℃基準で１１．６（核成長ｐＨ）になるまで、２５質量％水酸化ナトリウム水溶液の供給のみを一時停止し、ｐＨ値が１１．６に到達した後、再度２５質量％水酸化ナトリウム水溶液の供給を再開し、ｐＨ値を１１．６に制御したまま、４時間晶析を継続し、晶析を終了させた。晶析の終了後、生成物を水洗、濾過、乾燥させ、Ｎｉ０．３８Ｃｏ０．３２Ｍｎ０．３０（ＯＨ）２＋α（０≦α≦０．５）で表されるニッケルコバルトマンガン複合水酸化物粒子を得た。 (Example 1)
(Crystallization process)
First, the water in the reaction tank (60 L) was half-filled and stirred in the air atmosphere, while the temperature in the tank was set to 40 ° C., and 25 mass% sodium hydroxide aqueous solution and 25 mass% aqueous ammonia were added there. Was added in an appropriate amount to adjust the pH value of the liquid in the tank to 12.8 based on the liquid temperature of 25 ° C. and the ammonia concentration in the liquid to 10 g / L. To this, a 2.0 mol / L mixed aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate (Ni: Co: Mn = 38: 32: 30 in terms of metal element molar ratio) was added at a rate of 130 ml / min, did. At the same time, crystallization was carried out for 2 minutes and 30 seconds while adding 25 mass% aqueous ammonia and 25 mass% aqueous sodium hydroxide solution at a constant rate and controlling the pH value to 12.8 (nucleation pH). Thereafter, 25 mass% sodium hydroxide was added until the pH value reached 11.6 (nuclear growth pH) on the basis of the liquid temperature of 25 ° C. while flowing nitrogen gas and reducing the oxygen concentration in the reaction vessel to 2% by volume or less. After temporarily stopping the supply of the aqueous solution and the pH value reached 11.6, the supply of the 25 mass% sodium hydroxide aqueous solution was resumed, and the crystallization was performed for 4 hours while controlling the pH value to 11.6. Continuing to complete the crystallization. After completion of the crystallization, the product was washed with water, filtered and dried, and nickel cobalt manganese composite water represented by Ni 0.38 Co 0.32 Mn 0.30 (OH) 2 + α (0 ≦ α ≦ 0.5) Oxide particles were obtained.
（リチウム混合工程、焼成工程）
　得られた複合水酸化物粒子と、Ｌｉ／Ｍｅ＝１．０７となるように秤量した炭酸リチウムを、シェーカーミキサー装置（ウィリー・エ・バッコーフェン（ＷＡＢ）社製ＴＵＲＢＵＬＡ　ＴｙｐｅＴ２Ｃ）を用いて十分に混合し、リチウム混合物を得た。このリチウム混合物を空気（酸素：２１容量％）気流中にて９００℃で１０時間保持して焼成し、その後、解砕してリチウムニッケルコバルトマンガン複合酸化物粒子を得た。 (Lithium mixing process, firing process)
The obtained composite hydroxide particles and lithium carbonate weighed so as to be Li / Me = 1.07 are sufficiently mixed using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)). To obtain a lithium mixture. This lithium mixture was baked by being held at 900 ° C. for 10 hours in an air stream (oxygen: 21 vol%), and then pulverized to obtain lithium nickel cobalt manganese composite oxide particles.
（ホウ素混合工程、熱処理工程）
　さらに、得られた前記リチウム複合酸化物粒子と、オルトホウ酸を、熱処理後の正極活物質の組成を示す一般式（１）において、ｔ＝０．０３となるように秤量したオルトホウ酸を、シェーカーミキサー装置（ウィリー・エ・バッコーフェン（ＷＡＢ）社製ＴＵＲＢＵＬＡ　ＴｙｐｅＴ２Ｃ）を用いて十分に混合し、ホウ素混合物を得た。このホウ素混合物を空気（酸素：２１容量％）気流中にて２５０℃で１０時間保持して熱処理し、正極活物質を得た。 (Boron mixing process, heat treatment process)
Further, the obtained lithium composite oxide particles and orthoboric acid were weighed in the general formula (1) showing the composition of the positive electrode active material after the heat treatment so that t = 0.03. The mixture was sufficiently mixed using a mixer device (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a boron mixture. The boron mixture was heat-treated in an air stream (oxygen: 21% by volume) for 10 hours at 250 ° C. to obtain a positive electrode active material.
　得られた正極活物質の平均粒径、および〔（ｄ９０－ｄ１０）／平均粒径〕値、一次粒子の平均粒径、水溶性Ｌｉの測定結果等を表１に示す。また、正極活物質の走査電子顕微鏡（ＳＥＭ：日本電子株式会社製、ＪＳＭ－６３６０ＬＡ）による正極活物質の観察結果を図３に示す。得られた正極活物質をＸＰＳ（アルバック・ファイ社製、ＶｅｒｓａＰｒｏｂｅ　ＩＩ）で分析したところ、ホウ素のピークにリチウムとの化合を示す波形が確認され、一次粒子の表面にリチウムホウ素化合物が存在することが確認された。また、二次粒子内部のホウ素の存在について、ＦＥ－ＳＥＭに取り付けた軟Ｘ線発光分光装置（Ｓｏｆｔ　Ｘ－ｒａｙ　Ｅｍｉｓｓｉｏｎ　Ｓｐｅｃｔｒｏｓｃｏｐｙ；ＳＸＥＳ）によって分析した結果の一例を図４に示す。図４（Ａ）に示すように、一次粒子の中心部では、ホウ素の明確なピークが観察されなかったが、図４（Ｂ）に示すように、二次粒子内の粒界（一次粒子の表面）にホウ素を示すピークが観察され、ホウ素が存在することが確認された。 Table 1 shows the average particle diameter, [(d90-d10) / average particle diameter] value, average particle diameter of primary particles, measurement results of water-soluble Li, and the like of the obtained positive electrode active material. FIG. 3 shows the results of observation of the positive electrode active material using a scanning electron microscope (SEM: JSM-6360LA, manufactured by JEOL Ltd.). When the obtained positive electrode active material was analyzed with XPS (manufactured by ULVAC-PHI, VersaProbe II), a waveform indicating a combination with lithium was confirmed at the boron peak, and a lithium boron compound was present on the surface of the primary particles. Was confirmed. FIG. 4 shows an example of the result of analyzing the presence of boron in the secondary particles by a soft X-ray emission spectroscopy (SXES) attached to the FE-SEM. As shown in FIG. 4 (A), a clear peak of boron was not observed in the central part of the primary particle, but as shown in FIG. 4 (B), the grain boundary in the secondary particle (of the primary particle) A peak indicating boron was observed on the surface), and it was confirmed that boron was present.
（電池作成）
　得られた正極活物質５２．５ｍｇ、アセチレンブラック１５ｍｇ、およびポリテトラフッ化エチレン樹脂（ＰＴＦＥ）７．５ｍｇを混合し、１００ＭＰａの圧力で直径１１ｍｍ、厚さ１００μｍにプレス成形し、図６に示す正極（評価用電極）ＰＥを作製した。作製した正極ＰＥを真空乾燥機中１２０℃で１２時間乾燥した後、この正極ＰＥを用いて２０３２型コイン電池ＣＢＡを、露点が－８０℃に管理されたＡｒ雰囲気のグローブボックス内で作製した。負極ＮＥには、直径１７ｍｍ厚さ１ｍｍのリチウム（Ｌｉ）金属を用い、電解液には、１ＭのＬｉＣｌＯ４を支持電解質とするエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の等量混合液（富山薬品工業株式会社製）を用いた。セパレータＳＥには膜厚２５μｍのポリエチレン多孔膜を用いた。また、コイン電池は、ガスケットＧＡとウェーブワッシャーＷＷを有し、正極缶ＰＣと負極缶ＮＣとでコイン型の電池に組み立てた。得られた正極活物質の初期充放電容量および正極抵抗値の測定結果を表２に示す。 (Battery creation)
The obtained positive electrode active material 52.5 mg, acetylene black 15 mg, and polytetrafluoroethylene resin (PTFE) 7.5 mg were mixed and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. Evaluation electrode) PE was prepared. The produced positive electrode PE was dried at 120 ° C. for 12 hours in a vacuum dryer, and then a 2032 type coin battery CBA was produced using this positive electrode PE in an Ar atmosphere glove box in which the dew point was controlled at −80 ° C. Lithium (Li) metal having a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode NE, and the electrolyte solution is an equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO 4 as a supporting electrolyte ( Toyama Pharmaceutical Co., Ltd.) was used. As the separator SE, a polyethylene porous film having a film thickness of 25 μm was used. The coin battery had a gasket GA and a wave washer WW, and was assembled into a coin-type battery with the positive electrode can PC and the negative electrode can NC. Table 2 shows the measurement results of the initial charge / discharge capacity and the positive electrode resistance value of the obtained positive electrode active material.
　（実施例２）
　ホウ酸添加の熱処理温度を２１０℃としたこと以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Example 2)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 210 ° C. The evaluation results are shown in Tables 1 and 2.
　（実施例３）
　ホウ酸添加の熱処理温度を２９０℃としたこと以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Example 3)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 290 ° C. The evaluation results are shown in Tables 1 and 2.
　（実施例４）
　熱処理後の活物質を示す一般式（１）において、ｔ＝０．０２となるように秤量したオルトホウ酸をリチウム複合酸化物粒子と混合した以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 Example 4
In the general formula (1) indicating the active material after the heat treatment, the positive electrode active material was prepared in the same manner as in Example 1 except that orthoboric acid weighed so that t = 0.02 was mixed with the lithium composite oxide particles. It was evaluated as it was obtained. The evaluation results are shown in Tables 1 and 2.
　（実施例５）
　熱処理後の活物質を示す一般式（１）において、ｔ＝０．０４となるように秤量したオルトホウ酸をリチウム複合酸化物粒子と混合した以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Example 5)
In the general formula (1) indicating the active material after the heat treatment, the positive electrode active material was prepared in the same manner as in Example 1 except that orthoboric acid weighed so that t = 0.04 was mixed with the lithium composite oxide particles. It was evaluated as it was obtained. The evaluation results are shown in Tables 1 and 2.
　（比較例１）
ホウ酸添加しない以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Comparative Example 1)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that boric acid was not added. The evaluation results are shown in Tables 1 and 2.
　（比較例２）
　ホウ酸添加の熱処理温度を１５０℃としたこと以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。得られた正極活物質をＸＰＳ（アルバック・ファイ社製、ＶｅｒｓａＰｒｏｂｅ　ＩＩ）で分析したところ、ホウ素のピークにリチウムとの化合を示す波形が確認されなかった。この結果から、リチウムを含むホウ酸化合物が形成していないと考えられる。 (Comparative Example 2)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 150 ° C. The evaluation results are shown in Tables 1 and 2. When the obtained positive electrode active material was analyzed by XPS (manufactured by ULVAC-PHI, VersaProbe II), a waveform indicating a combination with lithium was not confirmed at the boron peak. From this result, it is considered that a boric acid compound containing lithium is not formed.
　（比較例３）
　ホウ酸添加の熱処理温度を３５０℃としたこと以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Comparative Example 3)
A positive electrode active material was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature for boric acid addition was 350 ° C. The evaluation results are shown in Tables 1 and 2.
　（比較例４）
　熱処理後の活物質を示す一般式（１）において、ｔ＝０．０１５となるように秤量したオルトホウ酸をリチウム複合酸化物粒子と混合した以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Comparative Example 4)
In the general formula (1) indicating the active material after the heat treatment, the positive electrode active material was prepared in the same manner as in Example 1 except that orthoboric acid weighed so that t = 0.015 was mixed with the lithium composite oxide particles. It was evaluated as it was obtained. The evaluation results are shown in Tables 1 and 2.
　（比較例５）
　熱処理後の活物質を示す一般式（１）において、ｔ＝０．０４５となるように秤量したオルトホウ酸をリチウム複合酸化物粒子と混合した以外は、実施例１と同様にして正極活物質を得るとともに評価した。評価結果を表１および表２に示す。 (Comparative Example 5)
In the general formula (1) indicating the active material after the heat treatment, the positive electrode active material was prepared in the same manner as in Example 1 except that orthoboric acid weighed so that t = 0.045 was mixed with the lithium composite oxide particles. It was evaluated as it was obtained. The evaluation results are shown in Tables 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
（評価結果）
　実施例で得られた正極活物質は、ホウ素を含まない比較例１の正極活物質と比較して、二次電池の正極に用いた際、いずれも正極抵抗が低減され、高い電池容量が得られる。また、実施例で得られた正極活物質は、いずれもペーストのゲル化が抑制される。 (Evaluation results)
When the positive electrode active material obtained in the examples was used for the positive electrode of a secondary battery as compared with the positive electrode active material of Comparative Example 1 containing no boron, the positive electrode resistance was reduced and a high battery capacity was obtained. It is done. Moreover, the positive electrode active materials obtained in the examples all suppress the gelation of the paste.
　また、図５は、ホウ素原料の添加量以外は、同様の条件で製造した実施例１、４、５及び比較例１、４、５の初期放電容量（Ａ）、正極抵抗（Ｂ）及び水溶性Ｌｉ量（Ｃ）の評価／測定結果について、示したグラフである。図５に示されるように、ホウ素の添加量が少ない場合（比較例１、２）、正極抵抗の低減が少なく、スラリーのゲル化が生じる。一方、ホウ素の添加量が多すぎる場合（比較例５）、正極抵抗の低減はみられるものの水溶性リチウム量が多くなり、スラリーのゲル化が生じる。また、ホウ素添加量が多い場合、リチウムニッケルコバルトマンガン複合酸化物からのリチウムの引き抜きが多くなり、Ｌｉ席占有率が低下して初期放電容量が低下している。 FIG. 5 shows initial discharge capacities (A), positive electrode resistances (B) and aqueous solutions of Examples 1, 4, 5 and Comparative Examples 1, 4, 5 produced under the same conditions except for the addition amount of the boron raw material. It is the graph shown about the evaluation / measurement result of the property Li amount (C). As shown in FIG. 5, when the amount of boron added is small (Comparative Examples 1 and 2), the positive electrode resistance is reduced little and gelation of the slurry occurs. On the other hand, when the amount of boron added is too large (Comparative Example 5), although the positive electrode resistance is reduced, the amount of water-soluble lithium increases and gelation of the slurry occurs. Moreover, when there is much boron addition amount, the drawing | extracting of lithium from lithium nickel cobalt manganese complex oxide increases, Li seat occupation rate falls and initial stage discharge capacity falls.
　また、比較例２で得られた正極活物質（熱処理温度：１５０℃）は、二次粒子表面の一次粒子にリチウムホウ素化合物が確認されず、スラリーのゲル化が生じている。また、比較例３で得られた正極活物質（熱処理温度：３５０℃）は、水溶性Ｌｉ量の増加と、ペーストのゲル化が見られる。さらに、熱処理温度が高いため、リチウムニッケルコバルトマンガン複合酸化物からのリチウムの引き抜きが多くなり、Ｌｉ席占有率が低下して初期放電容量が低下している。以上の結果から、本実施形態の正極活物質は、熱処理温度とホウ素原料の添加量を、適正な範囲に設定することにより、良好な出力特性及び高い電池容量と電極作製時のペーストのゲル化抑制とを両立した活物質が得られることがわかる。 Further, in the positive electrode active material (heat treatment temperature: 150 ° C.) obtained in Comparative Example 2, no lithium boron compound was confirmed on the primary particles on the surface of the secondary particles, and the gelation of the slurry occurred. Moreover, the positive electrode active material (heat treatment temperature: 350 ° C.) obtained in Comparative Example 3 shows an increase in the amount of water-soluble Li and gelation of the paste. Furthermore, since the heat treatment temperature is high, lithium extraction from the lithium nickel cobalt manganese composite oxide is increased, the Li seat occupancy is lowered, and the initial discharge capacity is lowered. From the above results, the positive electrode active material of the present embodiment has good output characteristics, high battery capacity, and gelation of the paste at the time of electrode preparation by setting the heat treatment temperature and the amount of boron raw material to an appropriate range. It can be seen that an active material that is compatible with suppression can be obtained.
　本実施形態の正極活物質を用いた非水系二次電池は、高出力及び高い電池容量を有するという優れた電気特性を示すことから、携帯電話やノート型パソコンなどの携帯電子機器、パワーツールなどに搭載される小型二次電池として好適に用いることができる。 Since the non-aqueous secondary battery using the positive electrode active material of the present embodiment exhibits excellent electrical characteristics such as high output and high battery capacity, portable electronic devices such as mobile phones and notebook computers, power tools, etc. Can be suitably used as a small-sized secondary battery mounted on the battery.
　なお、本発明の技術範囲は、上述の実施形態などで説明した態様に限定されるものではない。上述の実施形態などで説明した要件の１つ以上は、省略されることがある。また、上述の実施形態などで説明した要件は、適宜組み合わせることができる。また、法令で許容される限りにおいて、日本特許出願である特願２０１６－１７８２１７、及び本明細書で引用した全ての文献の内容を援用して本文の記載の一部とする。 Note that the technical scope of the present invention is not limited to the aspect described in the above-described embodiment. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the contents of Japanese Patent Application No. 2016-178217, which is a Japanese patent application, and all the references cited in this specification are incorporated as part of the description of this text.
１０…正極活物質
１…リチウム金属複合酸化物
２…一次粒子
３…二次粒子
４…リチウムホウ素化合物
５…中空部
ＰＥ…正極（評価用電極）
ＮＥ…負極
ＳＥ…セパレータ
ＧＡ…ガスケット
ＷＷ…ウェーブワッシャー
ＰＣ…正極缶
ＮＣ…負極缶 DESCRIPTION OF SYMBOLS 10 ... Positive electrode active material 1 ... Lithium metal complex oxide 2 ... Primary particle 3 ... Secondary particle 4 ... Lithium boron compound 5 ... Hollow part PE ... Positive electrode (electrode for evaluation)
NE ... Negative electrode SE ... Separator GA ... Gasket WW ... Wave washer PC ... Positive electrode can NC ... Negative electrode can

Claims (10)

  1. 　一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物を含む非水系電解質二次電池用正極活物質であって、
    　前記リチウムニッケルコバルトマンガン複合酸化物は、複数の一次粒子が凝集した二次粒子と、前記一次粒子表面の少なくとも一部に存在するリチウムを含むホウ素化合物と、を含み、前記一次粒子表面に存在する水溶性Ｌｉ量が、前記正極活物質全量に対して、０．１質量％以下である、非水系電解質二次電池用正極活物質。     General formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (in the above formula (1), M1 is an element other than Li, Ni, Co, Mn, B, −0 .05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5), and a lithium nickel cobalt manganese composite oxide having a hexagonal layered crystal structure. A positive electrode active material for a secondary battery,
    The lithium nickel cobalt manganese composite oxide includes secondary particles in which a plurality of primary particles are aggregated, and a boron compound containing lithium existing on at least a part of the surface of the primary particles, and is present on the surface of the primary particles. The positive electrode active material for nonaqueous electrolyte secondary batteries whose water-soluble Li amount is 0.1 mass% or less with respect to the said positive electrode active material whole quantity.
  2. 　前記正極活物質の平均粒径が３μｍ以上２０μｍ以下である請求項１に記載の非水系電解質二次電池用正極活物質。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein an average particle size of the positive electrode active material is 3 µm or more and 20 µm or less.
  3. 　前記一次粒子の平均粒径が０．２μｍ以上１．０μｍ以下である請求項１または請求項２に記載の非水系電解質二次電池用正極活物質。 3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein an average particle size of the primary particles is 0.2 μm or more and 1.0 μm or less.
  4. 　前記正極活物質の粒度分布の広がりを示す指標である〔（ｄ９０－ｄ１０）／平均粒径〕が０．６０以下である請求項１～請求項３のいずれか一項に記載の非水系電解質二次電池用正極活物質。 The non-aqueous electrolyte according to any one of claims 1 to 3, wherein [(d90-d10) / average particle size], which is an index indicating a spread of a particle size distribution of the positive electrode active material, is 0.60 or less. Positive electrode active material for secondary battery.
  5. 　前記二次粒子が、その内部に中空部を形成した中空構造を有する請求項１～４のいずれか一項に記載の非水系電解質二次電池用正極活物質。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the secondary particles have a hollow structure in which a hollow portion is formed.
  6. 　一般式（１）：Ｌｉ１＋ｓＮｉｘＣｏｙＭｎｚＢｔＭ１ｕＯ２+β（前記式（１）中、Ｍ１は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ、Ｂ以外の元素であり、－０．０５≦ｓ≦０．２０、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０．０２≦ｔ≦０．０４、０≦ｕ≦０．１、及び、０≦β≦０．５を満たす。）で表され、六方晶系の層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物を含む非水系電解質二次電池用正極活物質の製造方法であって、
    　一般式（２）：ＮｉｘＣｏｙＭｎｚＭ２ｕ（ＯＨ）２＋α（前記式（２）中、Ｍ２は、Ｌｉ、Ｎｉ、Ｃｏ、Ｍｎ以外の元素であり、０．１≦ｘ≦０．５、０．１≦ｙ≦０．５、０．１≦ｚ≦０．５、ｘ＋ｙ＋ｚ＋ｕ＝１、０≦ｕ≦０．１、及び、０≦α≦０．５を満たす。）で表されるニッケルコバルトマンガン複合水酸化物粒子を晶析により得る晶析工程と、
    　前記ニッケルコバルトマンガン複合水酸化物粒子に、リチウム以外の金属元素の原子数の合計に対するリチウムの原子数の比が０．９５以上１．２０以下となるように、リチウム化合物を混合してリチウム混合物を得るリチウム混合工程と、
    　前記リチウム混合物を、酸化性雰囲気中において、８００℃以上１０００℃以下の温度で５時間以上２０時間以下保持して焼成することにより、複数の一次粒子が凝集した二次粒子からなるリチウムニッケルコバルトマンガン複合酸化物粒子を得る焼成工程と、
    　前記リチウムニッケルコバルトマンガン複合酸化物粒子とホウ素原料とを混合してホウ素混合物を得るホウ素混合工程と、
    　前記ホウ素混合物を、酸化性雰囲気中において２００℃以上３００℃以下の温度で熱処理する熱処理工程と、を備え、
    　前記熱処理工程において、前記一次粒子表面に存在する水溶性Ｌｉ量が、前記熱処理前に対して、前記熱処理後に１．３倍以下となるように熱処理を行う、非水系電解質二次電池用正極活物質の製造方法。     General formula (1): Li 1 + s Ni x Co y Mn z B t M1 u O 2 + β (in the above formula (1), M1 is an element other than Li, Ni, Co, Mn, B, −0 .05 ≦ s ≦ 0.20, 0.1 ≦ x ≦ 0.5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0.02 ≦ t ≦ 0 0.04, 0 ≦ u ≦ 0.1, and 0 ≦ β ≦ 0.5), and a lithium nickel cobalt manganese composite oxide having a hexagonal layered crystal structure. A method for producing a positive electrode active material for a secondary battery, comprising:
    Formula (2): Ni x Co y Mn z M2 u (OH) 2 + α ( the formula (2), M2 is, Li, Ni, Co, an element other than Mn, 0.1 ≦ x ≦ 0. 5, 0.1 ≦ y ≦ 0.5, 0.1 ≦ z ≦ 0.5, x + y + z + u = 1, 0 ≦ u ≦ 0.1, and 0 ≦ α ≦ 0.5). A crystallization step for obtaining nickel cobalt manganese composite hydroxide particles by crystallization;
    A lithium mixture is prepared by mixing the nickel cobalt manganese composite hydroxide particles with a lithium compound such that the ratio of the number of lithium atoms to the total number of atoms of metal elements other than lithium is 0.95 or more and 1.20 or less. Obtaining a lithium mixing step;
    Lithium nickel cobalt manganese comprising secondary particles in which a plurality of primary particles are aggregated by holding the lithium mixture in an oxidizing atmosphere at a temperature of 800 ° C. to 1000 ° C. for 5 hours to 20 hours. A firing step to obtain composite oxide particles;
    A boron mixing step of mixing the lithium nickel cobalt manganese composite oxide particles and a boron raw material to obtain a boron mixture;
    A heat treatment step of heat-treating the boron mixture at a temperature of 200 ° C. or higher and 300 ° C. or lower in an oxidizing atmosphere,
    In the heat treatment step, the positive electrode active for a non-aqueous electrolyte secondary battery is subjected to heat treatment so that the amount of water-soluble Li present on the surface of the primary particles is 1.3 times or less after the heat treatment with respect to that before the heat treatment. A method for producing a substance.
  7. 　前記ホウ素原料が、酸化ホウ素およびホウ素のオキソ酸の少なくとも一つであることを特徴とする請求項６に記載の非水系電解質二次電池用正極活物質の製造方法。 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the boron raw material is at least one of boron oxide and boron oxo acid.
  8. 　前記ホウ素原料が、オルトホウ酸である請求項７に記載の非水系電解質二次電池用正極活物質の製造方法。 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the boron raw material is orthoboric acid.
  9. 　前記焼成工程で得られたリチウムニッケルコバルトマンガン複合酸化物粒子を解砕する解砕工程をさらに備えることを特徴とする請求項６～８のいずれか一項に記載の非水系電解質二次電池用正極活物質の製造方法。 The non-aqueous electrolyte secondary battery according to any one of claims 6 to 8, further comprising a crushing step of crushing the lithium nickel cobalt manganese composite oxide particles obtained in the firing step. A method for producing a positive electrode active material.
  10. 　正極と、負極と、セパレータと、非水系電解質とを備え、前記正極は、請求項１～５のいずれか一項に記載の非水系電解質二次電池用正極活物質を含む非水電解質二次電池。 A nonaqueous electrolyte secondary comprising a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein the positive electrode includes a positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5. battery.
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